does duration of nicotine replacement therapy use matter ... · background and objectives: little...

Does Duration of Nicotine Replacement Therapy Use Matter

in Quitting Smoking? A Longitudinal Study of Smokers

in the General Population

by

BO ZHANG

A thesis submitted in conformity with the requirements for the degree of

Doctor of Philosophy in Epidemiology (PhD)

Dalla Lana School of Public Health

The University of Toronto

© Copyright by Bo Zhang, 2013

ii

Does Duration of Nicotine Replacement Therapy Use Matter in Quitting Smoking?

A Longitudinal Study of Smokers in the General Population

Bo Zhang

Doctor of Philosophy in Epidemiology (PhD)

Dalla Lana School of Public Health

The University of Toronto

2013

Abstract

Background and Objectives: Little is known about the impact of nicotine replacement therapy

(NRT) use duration on smoking cessation in the general population. This study determines

whether duration of NRT use is associated with smoking cessation.

Methods: Data were from the Ontario Tobacco Survey longitudinal study of a population-based

cohort of baseline smokers who made serious quit attempts during 18 months of follow-up. The

association between NRT (any NRT, patches, or gum) use duration and smoking cessation

outcomes (short-term abstinence ≥1 month and long-term abstinence ≥12 months) was estimated

by Poisson regression, adjusting for all confounding variables.

Results: Among the 1,590 eligible smokers, 933 (59%) did not use any NRT, 535 (34%) used

NRT <8 weeks, and 112 (8%) used NRT ≥8 weeks at follow-up. The median duration of NRT

use was 14 days. A consistent “J” shape of associations between quit aid use duration and

smoking cessation outcomes (quit rates) was found. Using any NRT, patches, or gum <8 weeks

was generally associated with a lower likelihood of quitting, but using them ≥8 weeks was

generally associated with a higher likelihood of quitting, compared to not using them. Only using

patches for the recommended duration (≥8 weeks) was associated with a higher likelihood of

iii

short-term (relative risk, RR 1.74, 95% confidence interval, CI 1.21-2.50) and long-term (RR

2.62, 95% CI 1.25-5.50) abstinence at the end of 18 months of follow-up, compared to not using

patches. Using gum ≥8 weeks was not associated with short- or long-term abstinence at the end

of 18 months of follow-up.

Conclusions: Using nicotine patches for the recommended duration is associated with

successful short- and long-term abstinence in the general population. More efforts are needed to

encourage smokers to use nicotine patches for eight or more weeks when attempting to quit.

iv

Acknowledgments

It is a great pleasure to acknowledge my supervisor, Dr. Joanna Cohen, whom I thank especially

for thoroughness, guidance, and unfailing support.

I am most grateful to Dr. Roberta Ferrence, who inspired me to pursue my dream of Doctor of

Philosophy in Epidemiology (PhD). Dr. Ferrence was my supervisor during my course work for

my degree. I am also grateful for her great support and encouragement.

I thank my committee members, who have been very supportive. Dr. Susan Bondy has long been

an inspiration to me. Her classes in epidemiology have proved to be one of my best learning

experiences at the University of Toronto. Dr. Peter Selby proved to be a most thorough

researcher in nicotine replacement therapy and smoking cessation.

I am also grateful to the Ontario Tobacco Research Unit and Dalla Lana School of Public Health,

University of Toronto for supporting me throughout my candidature.

v

Dedication

To my husband Roland Yu and my daughter Sisi Yu

for their support and generosity,

which smoothed my path throughout this dissertation,

I am forever grateful.

&

To my parents

for encouraging me to pursue my dream

for so long

vi

Abbreviations

AIC: Akaike information criterion

ARR: adjusted relative risk

CATI: computer-assisted telephone interview

CI: confidence interval

CO: carbon monoxide

FTND: Fagerstrom test for nicotine dependence

GTA: greater Toronto area

ICR: interaction contrast ratio

ITC: International Tobacco Control

NRT: nicotine replacement therapy

NSNRT: non-standard NRT

OR: odds ratio

OTC: over the counter

OTS: the Ontario Tobacco Survey

QIC: Quasi-information criterion

RR: risk ratio or relative risk

SD: standard deviation

SRC: Survey Research Centre

SE: standard error

SRNT: Society for Research on Nicotine and Tobacco

VIF: variance inflation factor

vii

Table of Contents

Abstract .............................................................................................................................................................. ii

Acknowledgments ............................................................................................................................................. iv

Dedication .......................................................................................................................................................... v

Abbreviations .................................................................................................................................................... vi

List of Tables ..................................................................................................................................................... xi

List of Figures ................................................................................................................................................. xvi

List of Appendices .......................................................................................................................................... xvii

Chapter 1: Literature Review: Cigarette Smoking and Nicotine Replacement Therapy ................................... 1

1.1 The Burden of Smoking ............................................................................................................................... 1

1.2 Smoking Cessation ....................................................................................................................................... 1

1.3 Addictiveness of Cigarette Smoking ............................................................................................................ 2

1.4 Mechanism of NRT in Smoking Cessation .................................................................................................. 3

1.5 Is Long-Term NRT Use Necessary? ............................................................................................................ 3

1.6 NRT Effect on Smoking Cessation .............................................................................................................. 4

1.7 Measures of Smoking Cessation in the Literature ........................................................................................ 9

1.8 Measures of NRT Use in the Literature ...................................................................................................... 10

1.9 Research Gaps in NRT Effectiveness for Smoking Cessation in the General Population ......................... 11

Chapter 2: Objectives and Hypotheses ............................................................................................................. 14

2.1 Objectives and Research Questions ............................................................................................................ 14

2.2 Hypotheses ................................................................................................................................................. 15

Chapter 3: Methods .......................................................................................................................................... 16

3.1 Data Source and Study Design ................................................................................................................... 16

3.2 Criteria for Respondents Included in the Current Study ............................................................................ 17

3.3 Outcome Measures ..................................................................................................................................... 17

3.4 Measures of NRT Use Duration (Main Independent Variable) .................................................................. 18

3.5 Potential Confounding Variables and Effect Modifiers ............................................................................. 18

3.6 Data Analysis.............................................................................................................................................. 22

3.6.1 Descriptive Analysis .................................................................................................................. 22

3.6.2 Analyses of Associations ........................................................................................................... 22

a) Associations between NRT Quit Aid Use Duration and Quitting Outcomes ................................. 22

b) Testing for Confounders and Effect Modifiers .............................................................................. 24

viii

c) Handling Collinearity ..................................................................................................................... 25

d) Data Weighting .............................................................................................................................. 27

3.7 Statistical Power ......................................................................................................................................... 27

3.8 Sensitivity Analysis .................................................................................................................................... 28

3.9 Ethics .......................................................................................................................................................... 29

Chapter 4: My Role in This Project .................................................................................................................. 30

Chapter 5: Potential Scholarly Benefits and Public Health Implications ......................................................... 31

Chapter 6: Results............................................................................................................................................. 33

6.1 Descriptive Analysis ................................................................................................................................... 33

6.1.1 Respondents in the OTS Longitudinal Panel Study .................................................................. 33

6.1.2 Respondents and Quit Attempt Patterns, Lost to Follow-up, and Retention Rate ..................... 33

6.1.3 Comparison of Those Included in the Analysis and Those Lost to Follow-up ......................... 41

6.1.4 Baseline and Follow-up Characteristics of Respondents: Overall ............................................. 43

6.1.4.1 Overall sample (un-weighted) ................................................................................................ 43

6.1.4.2 Comparison of un-weighted and weighted samples ............................................................... 48

6.1.5 Baseline and Follow-up Characteristics of Respondents: By NRT Use Duration .................... 55

6.2 Descriptive Analysis of the Sensitivity Analysis ....................................................................................... 68

6.2.1 Comparison of Respondents between the Two Analyses .......................................................... 68

Chapter 7: Analyses of Associations of NRT Use Duration and Smoking Cessation ...................................... 76

7.1 Short-Term Abstinence (Continuous Quitting ≥1 Month) at the End of 18 Months of Follow-up ............ 76

7.1.1 by any NRT use duration ........................................................................................................... 76

7.1.2 by patch use duration ................................................................................................................. 79

7.1.3 by gum use duration .................................................................................................................. 81

7.2 Long-Term Abstinence (Continuous Quitting ≥12 Months) at the End of 18 Months of Follow-up ........ 83

7.2.1 By any NRT use duration .......................................................................................................... 83

7.2.2 By patch use duration ................................................................................................................ 85

7.2.3 By gum use duration .................................................................................................................. 87

7.3 Short-Term Abstinence (Continuous Quitting ≥1 Month) at Any Period of Follow-Up ........................... 89


ix

7.3.2 By patch use duration ................................................................................................................ 92

7.3.3 By gum use duration .................................................................................................................. 96

7.4 Long-Term Abstinence (Continuous Quitting ≥12 Months) at Any Period of Follow-Up ........................ 98


7.4.2 By patch use duration .............................................................................................................. 100

7.4.3 By gum use duration ................................................................................................................ 102

7.5 Summary of the Association between NRT Use Duration and Smoking Cessation ................................ 104

Chapter 8: Summary of the Sensitivity Analysis ............................................................................................ 108

Chapter 9: Discussion ..................................................................................................................................... 112

9.1 The Overall Impacts of NRT Use in Smoking Cessation ......................................................................... 112

9.1.1 Impacts of Any NRT in Smoking Cessation ........................................................................... 113

9.1.2 Impacts of Nicotine Patches in Smoking Cessation ................................................................ 116

9.1.3 Impacts of Nicotine Gum in Smoking Cessation .................................................................... 118

9.1.4 What Would Occur if NRT Users Were Categorized as Yes and No without Considering the

Use Duration? ................................................................................................................................... 119

9.1.5 Patterns of Quit Aid Use .......................................................................................................... 119

9.2 Findings in the Sensitivity Analysis ......................................................................................................... 123

9.3 Why the Likelihood of Abstinence Is Higher among Nicotine Patch Users Than Gum Users? .............. 127

9.4 Comparison to Recent Studies .................................................................................................................. 128

9.5 Methodology Considerations .................................................................................................................... 130

9.5.1 Potential Impact of Eligibility and Inclusion Criteria for Sample Selection ........................... 130

9.5.2 Potential Reverse Causality Issues .......................................................................................... 132

9.5.3 Analytical Decision: Why Poisson Regression Was Used ...................................................... 133

9.5.4 Reliability of Outcome Measures ............................................................................................ 135

9.5.5 Reliability of NRT Use Measures ........................................................................................... 136

9.5.6 Potential Issues around Linking NRT Use and A Quit Attempt ............................................. 137

9.5.7 Handling Missing Data ............................................................................................................ 138

9.5.8 Level of Nonresponse .............................................................................................................. 140

9.5.9 Representativeness of the OTS Sample ................................................................................... 140

x

9.5.10 Confounding Effects .............................................................................................................. 142

9.5.11 Modifying Effects .................................................................................................................. 145

9.5.12 Strengths of the Current Study .............................................................................................. 146

9.5.13 Limitations of the Current Study ........................................................................................... 147

9.6 Implications of the Current Study ............................................................................................................ 150

9.7 Suggestions for Further Studies ............................................................................................................... 153

Chapter 10: Conclusions ................................................................................................................................. 154

References ...................................................................................................................................................... 158

xi

List of Tables

Table 1. Summary of very common flaws in the past observational studies that have investigated the

association between NRT and smoking cessation ......................................................................................... 8

Table 2. Outcome measures of smoking cessation in the literature ............................................................ 10

Table 3. Data collection schedule and number of respondents who completed interviews for the

longitudinal smokers in the Ontario Tobacco Survey (OTS) ...................................................................... 17

Table 4. Potential confounders and modifying variables ............................................................................ 19

Table 5. Respondents and their serious quit attempt patterns at follow-up, OTS longitudinal study 2005-

2009 ............................................................................................................................................................. 37

Table 6. Baseline characteristics of those included and those lost to follow-up three for quitting outcomes

at the end of 18 months of follow-up, OTS longitudinal study 2005-2009 ................................................. 42

Table 7. Characteristics of respondents who made serious quit attempts at follow-up: un-weighted and

weighted, OTS longitudinal study 2005-2009 ............................................................................................. 49

Table 8. Characteristics of respondents who made serious quit attempts at follow-up: by NRT use

duration, OTS longitudinal study 2005-2009 .............................................................................................. 58

Table 9. Characteristics of respondents who made serious quit attempts at follow-up: by quitting

outcome, OTS longitudinal study 2005-2009 .............................................................................................. 64

Table 10. Comparison of respondents in the main and sensitivity analyses, OTS longitudinal study 2005-

2009 ............................................................................................................................................................. 70

Table 11. Crude Poisson regression analysis: association between any NRT use duration and short-term

abstinence (continuous quitting ≥1 month) at the end of 18 months of follow-up among baseline smokers

who made serious quit attempts at follow-up and were re-interviewed 18 months later (n=1,368), OTS

longitudinal study 2005-2009 ...................................................................................................................... 77

Table 12. Adjusted Poisson regression analysis: association between any NRT use duration and short-

term abstinence (continuous quitting ≥1 month) at the end of 18 months of follow-up among baseline

smokers who made serious quit attempts at follow-up and were re-interviewed 18 months later (n=1,368),

OTS longitudinal study 2005-2009 ............................................................................................................. 78

Table 13. Crude Poisson regression analysis: association between nicotine patch use duration and short-




Table 14. Adjusted Poisson regression analysis: association between nicotine patch use duration and

short-term abstinence (continuous quitting ≥1 month) at the end of 18 months of follow-up among

xii

baseline smokers who made serious quit attempts at follow-up and were re-interviewed 18 months later

(n=1,368), OTS longitudinal study 2005-2009 ........................................................................................... 80

Table 15. Crude Poisson regression analysis: association between nicotine gum use duration and short-




Table 16. Adjusted Poisson regression analysis: association between nicotine gum use duration and short-




Table 17. Crude Poisson regression analysis: association between any NRT use duration and long-term

abstinence (continuous quitting ≥12 months) at the end of 18 months of follow-up among baseline



Table 18. Adjusted Poisson regression analysis: association between any NRT use duration and long-term

abstinence (continuous quitting ≥12 months) at the end of 18 months of follow-up among baseline



Table 19. Crude Poisson regression analysis: association between nicotine patch use duration and long-

term abstinence (continuous quitting ≥12 months) at the end of 18 months of follow-up among baseline




long-term abstinence (continuous quitting ≥12 months) at the end of 18 months of follow-up among

baseline smokers who made serious quit attempts at follow-up and were re-interviewed 18 months later

(n=1,092), OTS longitudinal study 2005-2009 ........................................................................................... 86

Table 21. Crude Poisson regression analysis: association between nicotine gum use duration and long-




Table 22. Adjusted Poisson regression analysis: association between nicotine gum use duration and long-




xiii

Table 23. Crude Poisson regression analysis: association between any NRT use duration and short-term

abstinence (continuous quitting ≥1 month) at any period of follow-up among baseline smokers who made

serious quit attempts at follow-up (n=1,590), OTS longitudinal study 2005-2009 ..................................... 90

Table 24. Adjusted Poisson regression analysis: association between any NRT use duration and short-

term abstinence (continuous quitting ≥1 month) at any period of follow-up among baseline smokers who

made serious quit attempts at follow-up (n=1,590), OTS longitudinal study 2005-2009 ........................... 92

Table 25. Crude Poisson regression analysis: association between nicotine patch use duration and short-




short-term abstinence (continuous quitting ≥1 month) at any period of follow-up among baseline smokers

who made serious quit attempts at follow-up (n=1,590), OTS longitudinal study 2005-2009 ................... 95

Table 27. Crude Poisson regression analysis: association between nicotine gum use duration and short-



Table 28. Adjusted Poisson regression analysis: association between nicotine gum use duration and short-



Table 29. Crude Poisson regression analysis: association between any NRT use duration and long-term

abstinence (continuous quitting ≥12 months) at any period of follow-up among baseline smokers who


Table 30. Adjusted Poisson regression analysis: association between any NRT use duration and long-term

abstinence (continuous quitting ≥12 months) at any period of follow-up among baseline smokers who


Table 31. Crude Poisson regression analysis: association between nicotine patch use duration and long-

term abstinence (continuous quitting ≥12 months) at any period of follow-up among baseline smokers

who made serious quit attempts at follow-up (n=1,314), OTS longitudinal study 2005-2009 ................. 100


long-term abstinence (continuous quitting ≥12 months) at any period of follow-up among baseline

smokers who made serious quit attempts at follow-up (n=1,314), OTS longitudinal study 2005-2009 ... 101

Table 33. Crude Poisson regression analysis: association between nicotine gum use duration and long-



xiv

Table 34. Adjusted Poisson regression analysis: association between nicotine gum use duration and long-



Table 35. Crude quit rate by NRT quit aid use duration, OTS longitudinal study 2005-2009 ................ 105

Table 36. Crude quit rate by NRT quit aid use duration in the sensitivity analysis, OTS longitudinal

study .......................................................................................................................................................... 110

Table 37. Summary of population-based studies assessing NRT effectiveness in quitting smoking ....... 184

Table 38. Power calculation for short- and long-term quitting outcomes in the analysis for those who

made a serious quit attempt ....................................................................................................................... 197

Table 39. Agreement on cigarette smoking measures .............................................................................. 199

Table 40. Agreement on NRT use measures ............................................................................................ 200

Table 41. Crude and adjusted Poisson regression analyses of the aassociations between quit aid use (yes

vs. no) and quitting short- (≥1 month) and long-term (≥12 months) in the current study, OTS longitudinal

study 2005-2009 ........................................................................................................................................ 201

Table 42. Quit aid use patterns among those who made serious quit attempts at follow-up, OTS

longitudinal study 2005-2009 .................................................................................................................... 202

Table 43. Crude and adjusted Poisson regression analyses in the sensitivity analysis: association between

any NRT use duration and short-term abstinence (continuous quitting ≥1 month) at the end of 18 months

of follow-up among baseline smokers who made serious quit attempts or reduced smoking at follow-up

and were re-interviewed 18 months later (n=2,278), OTS longitudinal study 2005-2009 ........................ 208


patch use duration and short-term abstinence (continuous quitting ≥1 month) at the end of 18 months of

follow-up among baseline smokers who made serious quit attempts or reduced smoking at follow-up and

were re-interviewed 18 months later (n=2,278), OTS longitudinal study 2005-2009 ............................... 209


gum use duration and short-term abstinence (continuous quitting ≥1 month) at the end of 18 months of

follow-up among baseline smokers who made serious quit attempts or reduced smoking at follow-up and

were re-interviewed 18 months later (n=2,278), OTS longitudinal study 2005-2009 ............................... 210


any NRT use duration and short-term abstinence (continuous quitting ≥1 month) during any period of

follow-up among baseline smokers who made serious quit attempts or reduced smoking at follow-up

(n=2,695), OTS longitudinal study 2005-2009 ......................................................................................... 211


patch use duration and short-term abstinence (continuous quitting ≥1 month) during any period of follow-

xv

up among baseline smokers who made serious quit attempts or reduced smoking at follow-up (n=2,695),

OTS longitudinal study 2005-2009 ........................................................................................................... 212


gum use duration and short-term abstinence (continuous quitting ≥1 month) during any period of follow-

up among baseline smokers who made serious quit attempts or reduced smoking at follow-up (n=2,695),

OTS longitudinal study 2005-2009 ........................................................................................................... 213

Table 49. Representativeness of the OTS sample to the CCHS 2007 survey population ......................... 214

Table 50. Adjusted RRs from Poisson regression for quitting outcomes at the end of 18 months of follow-

up among those who made a serious quit attempt at follow-up with complete follow-up data ................ 216

Table 51. Comparison between smokers using gum and patches only (not using other NRT products)

among those who made at least one serious quit attempt at follow-up, OTS longitudinal study 2005-2009

................................................................................................................................................................... 218

Table 52. Comparison between smokers using gum only ≥8 weeks and using patches only ≥8 weeks (not

using other NRT products) among those who made at least one serious quit attempt at follow-up, OTS

longitudinal study 2005-2009 .................................................................................................................... 221

xvi

List of Figures

Figure 1. Flow diagram for analysis of short-term abstinence on longitudinal respondents who made at

least one serious quit attempt at follow-ups one, two, or three and were re-interviewed at follow-up three

(having at least six months of follow-up after making a serious quit attempt), OTS longitudinal study

2005-2009 .................................................................................................................................................... 35

Figure 2. Flow diagram for analysis of long-term abstinence on longitudinal respondents who made at

least one serious quit attempt at follow-ups one or two and were re-interviewed at follow-up three

(having at least 12 months of follow-up after making a serious quit attempt), OTS longitudinal study

2005-2009 .................................................................................................................................................... 36

Figure 3. Summary of findings of short- and long-term quitting outcomes by quit aid use duration, main

analysis ...................................................................................................................................................... 107

Figure 4. Summary of findings of the short-term quitting outcome by quit aid use duration, sensitivity

analysis ...................................................................................................................................................... 111

Figure 5. Flow diagram for the questions in the OTS study to identify those who made a serious attempt

to quit at follow-up .................................................................................................................................... 189

Figure 6. Flow diagram for the questions in the OTS study to identify those who made a serious attempt

to quit and those who reduced smoking at follow-up, sensitivity analysis ............................................... 205

Figure 7. Flow diagram for analysis of longitudinal respondents at 6-, 12- and 18-month follow-ups with

valid data on smoking at baseline and follow-up, sensitivity analysis ...................................................... 207

xvii

List of Appendices

Appendix 1. Summary of Population-Based Studies ............................................................................... 184

Appendix 2. Questions and Variables Used in Identification of Participants ........................................... 188

Appendix 3. Questions and Variables Used in Identification of Outcome Measures and NRT Use ........ 190

Appendix 4. Determination of Variables for Potential Confounding Factors and Effect Modifiers ........ 192

Appendix 5. Power Calculation ................................................................................................................ 197

Appendix 6. Assessment of Reliability of Measures for the Outcome and NRT Use .............................. 199

Appendix 7. Association between NRT Use (yes vs. no) and Smoking Cessation of Poisson Regression

................................................................................................................................................................... 201

Appendix 8. NRT Use Patterns in the Analysis for Those Who Made A Serious Quit Attempt ............. 202

Appendix 9. Abstract for the 7th National Conference on Tobacco or Health .......................................... 203

Appendix 10. Sensitivity Analysis ........................................................................................................... 205

Appendix 11. Examination of Representativeness ................................................................................... 214

Appendix 12. Analyses for Smokers with Complete Data in the Analysis for Those Who Made A Serious

Quit Attempt .............................................................................................................................................. 215

Appendix 13. Comparison between Smokers Using Gum Only and Using Patches Only in the Current

Study .......................................................................................................................................................... 217

1

Chapter 1: Literature Review: Cigarette Smoking and Nicotine Replacement Therapy

1.1 The Burden of Smoking

Tobacco use imposes a huge and growing public health burden worldwide.1 It has been estimated

that smoking is responsible for five million deaths annually, and this number will rise to more

than eight million deaths annually by 2030.2 With current trends, approximately 500 million

people alive today will die prematurely as a result of tobacco use, with one billion deaths from

tobacco expected during this century.1

Cigarette smoking remains the leading cause of preventable mortality and morbidity in Canada.3

A Canadian study4 estimated that in 2002 in Canada cigarette smoking was responsible for over

37,000 deaths (constituted 17% of all deaths), and smoking-attributable cost for acute care

hospital days was over $2.5 billion. Although the prevalence of smoking in Canada has been

declining in the past decade, 17% of the Canadian population aged 15 years and older were

current smokers in 2010 (about 4.7 million smokers) according to the most recent Canadian

Tobacco Use Monitoring Survey.5 It is a major public health goal to reduce smoking related

mortality and morbidity.

1.2 Smoking Cessation

Research indicates that smoking cessation provides rapid health benefit.6 It is well documented

that adult smokers who quit (even after many years of smoking) reduce their risk for premature

death and other smoking-related health consequences.7-10 The most significant is a sharp

reduction in mortality, since smokers on average die 13 to 14 years earlier than non-smokers.11

Research has found that all-cause mortality approaches that of people who never smoked after 10

to 15 years of abstinence,12 or by quitting before the age of 35 years.13

Considerable effort has been focused on identifying mechanisms to assist smokers to quit. At the

population level, tobacco taxation,14-17 smoke-free environments,18-21 package warnings22-24 and

2

mass media campaigns25-27 have been found to be useful strategies for smoking cessation. At the

individual level, counselling and behavioural interventions and pharmaceutical therapies are

commonly used to assist quitting.28, 29 The vast majority of smokers wish to quit. For instance,

almost half of Canadian daily smokers aged 15 and older tried to quit in the last year according

to the 2008 Canadian Tobacco Use Monitoring Survey.30 However, many find it difficult to quit

smoking. Research has indicated that 80-90% of those who attempt to quit smoking relapse

within a year of their quit dates, 31-33 in large part due to addiction to nicotine in cigarettes.34

1.3 Addictiveness of Cigarette Smoking

It is widely acknowledged that cigarette smoking is addictive. Smoking is primarily maintained

by an addiction to nicotine.35-37 Smokers are addicted to cigarette smoking because it delivers

nicotine to the brain in a convenient and flexible way that allows smokers to control the dose

they receive.38

Many theories have been used to describe the addiction mechanism. One common component is

the involvement of dopamine. Nicotine from each puff on a cigarette acts on nicotinic

cholinergic receptors in the brain to release dopamine and other neurotransmitters that sustain

addiction.39 Dopamine release in the core of the nucleus accumbens appears to act to generate

stimulus-impulse associations.40 In the presence of smoking cues, nicotine causes one of the most

basic levels of human motivation (according to the West’s PRIME theory,41 human behaviour

can be explained by a five level motivational system) that generates the impulse to smoke. The

impulse to smoke does not require any anticipated pleasure, satisfaction, or relief.41 Research

also reveals that smokers have impaired functioning of the low-level brain mechanisms that

underlie inhibition during nicotine withdrawal. Thus, smokers who try to quit, not only

experience the impulse to smoke in the presence of smoking cues, but also have a reduced

capacity to inhibit smoking.38 It is estimated that 58% of Canadian daily smokers in 2008 were

nicotine addicted based on the heaviness of smoking index (≥3).42 Susceptibility to nicotine

addiction can vary by enzyme polymorphisms that determine an individual’s ability to

metabolize nicotine.43 When quitting smoking, individuals may experience withdrawal

3

symptoms including dysphoria, insomnia, irritability, anxiety, diminished concentration,

restlessness, increased appetite, decreased heart rate and weight gain.34 When withdrawal

symptoms occur, smokers feel the cravings (i.e., the urge to smoke and seek reward from

smoking).

1.4 Mechanism of NRT in Smoking Cessation

It has been hypothesized that factors that decrease the bioavailability of nicotine would increase

an individual’s cravings and decrease the likelihood of cessation as more of the drug is needed to

achieve a given level of dopamine.44 This has led to the development of smoking cessation

treatment methods that emphasize nicotine replacement.45 Nicotine replacement therapies

(NRTs) can mimic or replace the effects of nicotine from tobacco,37 assisting with smoking

cessation. Several ways have been identified for NRTs to facilitate smoking cessation. First,

NRTs can relieve the withdrawal symptoms associated with stopping smoking, which is the

principal action of NRTs. Second, NRTs provide positive reinforcement (such as enhancement of

mood or functioning), which has stress-relieving effects. Third, NRTs can desensitize nicotinic

receptors, which results in a reduced effect of nicotine from cigarettes. This means that when a

quitter lapses to smoking while on NRT, the cigarette is less satisfying and the quitter is less

likely to resume smoking.37 Thus NRT makes it easier for smokers to quit smoking and avoid a

relapse.

1.5 Is Long-Term NRT Use Necessary? As mentioned above, cigarette smoking is addictive. Cigarette use modifies brain function in

critical ways and prolonged cigarette use causes pervasive changes in brain function that persist

long after the individual quits smoking.46 For most people, tobacco addiction is a chronic,

relapsing disorder, rather than an acute illness.46 This means that total abstinence of the rest of

one’s life is a relatively rare outcome from a single treatment episode. Tobacco addiction must

be approached more like other chronic diseases, such as diabetes and chronic hypertension.46

Short-term treatment of NRT can treat the physical dependency caused by cigarette smoking, but

the roots of psychological dependency are often much deeper. When nicotine gum was available

by prescription only, smokers were instructed to use the medication for 6 months.47 The shorter

4

treatment duration for over the counter (OTC) NRT was perhaps due to concerns about the abuse

and dependence potential.47 Research has indicated that prolonged use of NRT or other

medications may reduce progression of lapses to relapse, reduce the likelihood or severity of

prolonged or labile withdrawal, and reduce anhedonia associated with withdrawal.48-53 This

evidence indicates that prolonged NRT or other medication use on smoking cessation may be

necessary.

1.6 NRT Effect on Smoking Cessation

The 2009 Cochrane review54 concluded that NRT could increase smoking cessation rates by 50%

to 70%, compared to placebo. The review included 132 randomized clinical trials with over

40,000 participants with follow-up periods generally between 6 and 12 months. The relative risk

(RR) of abstinence for any form of NRT relative to control was 1.58 (95% confidence interval

(CI) 1.50-1.66), and the pooled RR for each type were 1.43 (95% CI 1.33-1.53; 53 trials) for

nicotine gum, 1.66 (95% CI 1.53-1.81; 41 trials) for nicotine patches, 1.90 (95% CI 1.36-2.67; 4

trials) for nicotine inhaler, and 2.00 (95% CI 1.63-2.45; 6 trials) for oral tablets/lozenges.54

Most clinical trials of NRT evaluated efficacy in conjunction with substantial behavioural

intervention.55 One issue from clinical trials is whether using NRT without regular contact would

achieve the same effectiveness in the real world as in the trials. The efficacy of NRT in clinical

trials may not be generalizable to the general population. In addition, some have argued that

people who volunteer to test NRTs, but who are randomly assigned to get a placebo instead of

NRTs they wanted may not be reasonably compared to people who decide to quit smoking

without NRTs.56 Furthermore, research finds that of the Cochrane selected randomized

controlled trials57 of NRT only 22% of non-industry trials (n=9) reported significant cessation

effects, while 51% of industry-funded trials (n=25) did so.58, 59 There is a need for research on

the effectiveness of NRT in the general population.

Only a few studies have assessed the effectiveness of NRT in the general population and the

results from these studies have been inconsistent. Several population-based cross-sectional60 and

5

cohort studies61, 62 have shown negative or unbeneficial impact of NRT use compared with

unaided or non-pharmaceutical aided cessation. Buck et al.60 found that nicotine gum and patch

users were less likely to have given up smoking than non-users, using a cross-sectional random

and representative general adult population in England in 1995. Alberg et al.61 found that 30% of

ever NRT users had quit smoking, compared to 39% of nonusers. The study used a non-

representative sample of smokers in the general population. Ferguson et al.62 compared the effect

of NRT and bupropion to non-pharmaceutical aided cessation, using a cohort of smokers

(n=2,069). This study62 found that the continuous cessation rate at 52 weeks (validated by carbon

monoxide, CO) was 15.2% for NRT only, 14.4% for bupropion only, 7.4% for both NRT and

bupropion, and 25.5% for willpower without pharmaceutical aids (i.e., did not use any quit

aids).62 The study participants were not a representative sample of the population.

A few population-based cross-sectional63, 64 and cohort studies65-67 report NRT is effective (i.e.,

increased the cessation rate), but mostly in the short term. Pierce et al.63 assessed smoking

cessation and pharmaceutical aid use in the general California population [population-based

California Tobacco Surveys of 1992 (n=5247), 1996 (n=9725) and 1999 (n=6412)]. The main

outcome measures included rates of cessation attempts (≥ 1 day) among smokers in the last year

and cessation duration for recent former smokers (12 months ago but not currently) between the

survey date and the last date they smoked regularly. For the duration of cessation, the study used

Cox proportional hazards regression analyses, adjusted for age, sex, race, education, and

cigarette consumption a year earlier. The study found that use of NRT increased short-term

cessation success in moderate to heavy smokers in each survey year. Long-term cessation effect

of NRT was only found in 1992 and 1996 (before NRT became widely available over-the-

counter, August 1996), but not in 1999. There was no information on quit rate by NRT use on

either short term or long term cessation. No definition of short-term and long-term quit was

provided. The longest duration of cessation was less than one year. It is unclear if quitters used

any behavioural support (e.g., self-help materials and motivational support). This study raised an

important question that NRT without behavioural support may not be effective in the general

population.

6

Zhu et al.64 used the 1996 California Tobacco Survey, a random sample of 4,480 individuals (18

years or older) who tried to quit smoking in the 12 months before the survey, to compare the

success quit rate of those who used assistance with those who did not. The study found that those

who used assistance had a greater quit rate (>24 hours) at survey than those who did not use

assistance (26.7% vs. 16.3%, p<0.001). The 12 month abstinence rate was significantly higher

among assistance users (NRT, counselling, and other help) than non-users, adjusted for gender,

age, education, ethnicity, and cigarettes per day. The study also found no significant differences

in quit rate by type of assistance used (self-help, 20.2%; counselling, 21.5%; NRT, 30.3%; and

counselling and NRT, 23.7%; for all, p>0.05). However, no independent analysis for NRT use

compared to non-users for 12 month abstinence was reported in this study. Thus, the

effectiveness of NRT was based on quit attempt > 24 hours, rather than long-term quit.

Swartz et al.65 assessed quitting outcomes (7-day and 30-day point prevalence and 6-month

abstinence) among those with NRT plus counselling and those with counselling alone in smokers

who registered with the Tobacco HelpLine in Maine November 2003 to January 2004 (n=535),

six months after assistance. The study reported that intent-to-treat quit rates (30-day point

prevalence) at 6 months were 12.3% (95% CI 8.1–17.6) for counselling alone, and 22.5% (95%

CI 19.1–26.3) for counselling plus NRT, and the 6-month abstinence rates were 6.9% for

counselling alone and 12.5% for counselling plus NRT. This is a descriptive study, in which

there was no adjustment for differences of demographics and tobacco dependence. In addition,

those who received NRT obtained more counselling service than those not receiving NRT. The

study participants were not a representative sample of the general population.

Miller et al.66 assessed the smoking status of 1,305 randomly sampled NRT recipients and a non-

randomly selected comparison group of eligible smokers who, because of mailing errors, did not

receive the treatment from a large-scale distribution program of free nicotine patches. The study

found that at 6 months, more NRT recipients than comparison group members successfully quit

smoking (7-day point prevalence) (33% vs. 6%, p<0.0001), and this difference remained

significant after adjustment for demographic factors and amount smoked (odds ratio, OR=8.8,

7

95% CI 4.4-17.8) in logistic regression analysis. This study recruited participants from toll-free

quitline users, rather than a representative sample of the general population. NRT users received

more behavioural support than non-users.

West et al.67 used a multinational cohort study with data collection by the internet to assess the

effectiveness of NRT. Follow-up assessments were carried out every 3 months. There were two

phases in this study. In phase one, 492 smokers who made a quit attempt without formal

behavioural support or bupropion in the first 3-month follow-up period were identified, and 357

were followed up for a further 6 months. In phase two, among the 906 smokers making quit

attempts, 732 were followed up. The main outcome was self-report of abstinence throughout

both the 3-month periods following the quit date. The study found that the ORs comparing

abstinence for 6 months in those using and those not using NRT, adjusting for nicotine

dependence in logistic regression analysis, were 3.0 (95% CI 1.2-7.5) for the phase one sample

and 2.1 (95% CI 1.0-4.1) for the phase two sample. The difference in success rates between those

using NRT and those not using it, adjusted for the Fagerstrom test for nicotine dependence score,

was 6% in the phase one sample and 3.7% in the phase two sample. The sample was not

representative of the general population, and previous quit attempts were not controlled for.

The effectiveness of NRT for long term cessation (continuous abstinence for 6 months, or 7 day

point prevalence at 6 months) were all from non-representative population studies.62, 65-67 The

majority of these studies (75%, three out four studies) were free NRT distribution studies, in

which all participants received behavioural support. There was a tendency that those who

received NRT received more behavioural support than those who did not receive NRT in these

free-NRT distribution programs. Results from these studies may not be generalizable to the

general population. Among the three studies60, 63, 64 using the representative general population,

two60, 64 found a negative effect of NRT on smoking cessation. The only one63 that found NRT

associated with long-term cessation (up to 12 months) was before the availability of over the

counter (OTC) NRT (behavioural support provided), but not after the availability of OTC NRT

(no behavioural support).

8

Only one population-based study68 assessed the association between NRT use duration (any use

and use >6 weeks) and relapse. The study68 found that the odds of relapse were unaffected by the

use of NRT for >6 weeks either with (p=0.117) or without (p=0.159) professional counselling

and were highest among prior heavily dependent persons who reported NRT use for any length

of time without professional counselling (OR=2.68). However the study did not use the

recommended duration of 8 weeks to categorize the NRT use groups; and the commonly used

forms of nicotine patches and gum were not examined separately. According to the 2009

Cochrane review,54 it appears that nicotine patches may be more effective than nicotine gum

(Summary of the NRT effect in the population-based studies can be found in Appendix 1).

The very common flaws in past observational studies are presented below (Table 1).

Table 1. Summary of very common flaws in the past observational studies that have investigated the association between NRT and smoking cessation Common Flaws Explanation Potential effect on the outcome Misclassification (e.g., recall bias)

NRT use was measured as ever use, for the last quit attempt, and for the most recent quit attempt in the last year. Those who quit long time ago might not be able to recall NRT use. Even for those who tried to quit in the last year might not recall NRT use for a very short period of NRT use. Those who had serious side effects and discontinued use of NRT might be able to recall NRT use.

If those who used NRT and quit but did not recall use of NRT, the association between NRT use and smoking cessation would be attenuated toward null. If more people with side effects from NRT use could recall NRT use than those who used NRT and quit without side effects, the association between NRT use and smoking cessation would be attenuated too. Among NRT users, if more people who quit could recall of NRT use than those who did not quit, the association between NRT use and smoking cessation would be moved away from null (i.e., higher smoking cessation rate in NRT users than non-users).

Selection bias 1) Studies failing to detect a long-term NRT benefit may be explained at least partly by self-selection of NRT use, if NRT is used by more failure-prone smokers; 2) On the other hand, participants who are highly motivated to be helped are more likely to quit smoking among studies that use non-representative samples, especially in free NRT programs.

1) The association between NRT use and cessation would be attenuated toward null. 2) Those who use NRT to quit smoking with high expectation and motivation are more likely to have a higher likelihood to quit than those with low expectation and motivation. Thus, the association between NRT use and cessation would be moved away from null.

9

Confounding effect

Several studies included behavioural support as part of the intervention and NRT recipients were provided more behavioural support than those who did not receive NRTs. In addition, tobacco dependence is a potential confounding factor, but was not controlled for in several studies.

Those who used NRTs but received more behavioural support than those who did not use NRTs would overestimate the effect of NRTs on cessation, if the confounding effect of behavioural support was not controlled for. If those who used NRTs were those who had higher tobacco dependence than those who did not use NRTs, the effect of NRTs would be underestimated, if this confounding factor was not controlled for and high dependence would make quitting more difficult.

Generalization issue

Several studies used a non-representative sample, especially among those studies providing free NRTs.

Generalizability (external validity) may be questionable. Findings of the study may only reflect a unique population and therefore cannot be generalized to others. However, this is not a critical problem in studies assessing the association between NRT use and smoking cessation, because the scientific goal is to move from time- and place-specific observations to an abstract “universal” hypothesis, such as “NRT increases smoking cessation”.

1.7 Measures of Smoking Cessation in the Literature

The majority of outcome measures for smoking cessation in clinical trials included in the 2009

Cochrane review54 was continuous or sustained abstinence at 12 months (n=64, including two

studies counted as four trials), followed by continuous or sustained abstinence at 6 months

(n=15), point prevalence at 6 months (n=15) and at 12 months (n=13), undefined abstinence at 6

months (n=7) and at 12 months (n=8), and others (e.g., prolonged abstinence at 6 or 12 months,

sustained abstinence at 2 years). The majority of the cessation outcomes were validated with

expired CO (n = 99), others by plasma thiocyanate, independent observers, cotinine, blood

carboxyhemoglobin, and non-validation (n=10).

In general population studies, outcome measures consisted of unclearly defined, point prevalence

abstinence (7 or 30 days), quit attempt (≥24 hrs), abstinence at 3 and 6 months, and sustained

abstinence at 52 weeks. Only one study used CO validation. The outcome measures for smoking

cessation are summarized in the table below (Table 2).

10

Table 2. Outcome measures of smoking cessation in the literature

Study type Outcome measure Validation etc. Clinical trials

Abstinence† (>1 wk or not defined) at 6m,69-75 12m,76-83 and 13m84

Carbon monoxide (CO), plasma thiocyanate, or no validation

Continuous or sustained abstinence‡ at 5m,85 6m,86, 87 88-100 10.5m,101 12m102-110 111-160,161-163 (up to 3 cigs/wk allowed in 3 studies,86, 163, 164 or lapse-free), 13m,165 and 2 yr166

CO <10 ppm (generally), venous carboxyhaemoglobin, saliva or urinary cotinine, or no validation

Point prevalence (PP) abstinence§ (7day or not stated) at 6m (incl. 26wks),167-181 36wks,182 12m,183-195 and 16m196

Plasma cotinine, CO, or no validation

Prolonged abstinence# at 6m197, 198and 12m199 Self-report or CO Cross sectional study

Quitters at interview (not clearly defined), cessation attempts (≥ 1 day), and duration of cessation (last date of regular smoking to the date of interview)63, 64

Self-report no validation

Cohort study

Quitters (not clearly defined),61 sustained cessation at 52 wks,62 7d, 30d, and continuous abstinence at 6m,65 successful quit attempt (≥24h) and 7d point prevalence abstinence,66 and abstinence for 3m and 6m67

Self-report or no validation (only one study62 used CO validation)

Definitions of abstinence in the Cochrane review54 are listed below. † Abstinence - “A period of being quit, i.e., stopping the use of cigarettes or other tobacco products. May be defined in various ways.” ‡ Continuous or sustained abstinence - “A measure of cessation often used in clinical trials involving avoidance of all tobacco use since the quit day until the time the assessment is made. The definition occasionally allows for lapses. This is the most rigorous measure of abstinence.” § Point prevalence abstinence - “A measure of cessation based on behaviour at a particular point in time, or during a relatively brief specified period, e.g., 24 hours, 7 days. It may include a mixture of recent and long-term quitters.” # Prolonged abstinence - “A measure of cessation which typically allows a ’grace period’ following the quit date (usually of about two weeks), to allow for slips/lapses during the first few days when the effect of treatment may still be emerging.”

1.8 Measures of NRT Use in the Literature

The effect of NRT on smoking cessation has been examined by different forms of NRT,

including nicotine patches, nicotine gum, nicotine inhaler, nicotine tablets/lozenges, nicotine

intranasal spray, and combinations of NRT products. Some recent reviews have indicated that

combination therapies with one or two formulations of NRT are superior to a single form of

NRT.54, 200 The effect of NRT duration has been examined in some clinical trials. The 2009

Cochrane review54concluded that the effect of NRT was largely independent of the duration of

therapy.

11

In general population studies, measures for NRT use included ever use of NRT (including gum

and patches),60, 61 NRT use (gum and patches) for the last quit attempt,64 NRT use for their most

recent quit attempt in the last year,63 free 6-week courses of NRT patches,66 brief advice from

health professionals and NRT or bupropion,62 a continuous supply of NRT with no <15 days of

disruption in drug supply,65 and NRT use in the past three-months.67

1.9 Research Gaps in NRT Effectiveness for Smoking Cessation in the General Population

In general, NRT products should be used for 8 to 12 weeks.201 Studies have shown that

compliance with recommended duration of treatment occurs among 50% or fewer NRT users.55,

202-211 Poor adherences to NRT regimens outside clinical trials may explain the apparent lesser

effectiveness of NRT in the general population.

The 2009 Cochrane review54 compared the effect of duration of NRT use on smoking cessation.

Based on pooled results, the Cochrane review found that the relative risk (RR) was 1.60 (95% CI

1.43-1.79) for providing nicotine patches more than eight weeks (26 trials) and 1.89 (95% CI

1.64-2.18) for providing nicotine patches eight weeks or less (15 trials, including one study with

two trials),69, 76, 79-81, 88, 99, 100, 163, 168, 169, 176, 178, 192 compared to the placebo or control group.

However, among the 15 trials with nicotine patches for eight weeks or less, only two trials

provided nicotine patches for four weeks or less88, 163 (one with three weeks), others provided

nicotine patches for at least six weeks (eight trials with six weeks and five trials with eight

weeks). Participants from the two trials with four weeks or less weighted only 5.9% of the

pooled results of the 15 trials. Therefore, the pooled results for NRT use for eight weeks or less

were largely based on those using NRT for at least six weeks. The outcomes from the 15 trials

consisted of a mix of smoking cessation measures, including point prevalence (seven days) at six

months and 12 months, abstinence at 12 months (not clearly stated), and continuous abstinence at

six months and 12 months. Furthermore, one trial163 allowed smoking up to three cigarettes per

week for sustained abstinence and 8 trials provided high level of support (e.g., nine weekly group

sessions in one trial76). The Cochrane review also assessed the effect of duration of NRT

between long and short time periods. The RR was 1.05 (95% CI 0.88-1.26) for 28 weeks versus

12

12 weeks of nicotine patches (one trial, n=2,861), 0.61 (95% CI 0.26-1.41) for 12 weeks versus

three weeks of nicotine gum (one trial,85 n=98), 1.03 (95% CI 0.62-1.71) for 12 weeks versus six

weeks of patches (one trial,70 n=140), and 0.93 (95% CI 0.52-1.67) for six weeks versus three

weeks of patches (one trial,69 n=80). The comparison between long and short durations of NRT

use was based only on a few trials, and some RRs of the comparison trials had wide confidence

intervals.

Although the 2009 Cochran review54 concluded that the effect of NRT was largely independent

of the duration of therapy, the minimum duration of therapy was three weeks in the clinical trials

included in its review. No comparison between NRT use for three weeks and not using NRT was

conducted in the Cochrane review. The effect of NRT use reported for eight weeks or less was

mainly based on trials that provided nicotine patches for at least six weeks. Almost all trials

provided nicotine patches in those assessing the effect of duration (only one trial provided

nicotine gum). It is not clear if the effect of duration would be similar for the combined form of

NRT (i.e., including gum, patches, inhaler, and lozenges).

In the general population, it has been reported that the median duration of NRT use ranged from

9.8 days211 to 14 days.63, 212 Burns et al.211 found that the duration was shorter for those who

resumed smoking (10.1 days) and those who said NRT did not help (6.5 days), but longer for

those who discontinued NRT because they quit smoking (20.7 days). This may suggest that three

weeks of NRT use may be long enough to assist NRT users to quit smoking. This study211 also

found that only 11.7% of those attempting to quit used NRT for eight weeks or more (the

recommended duration for NRT use). However, this was a descriptive analysis with regard to

duration of NRT use in this study.211 The study’s focus was to examine reasons for discontinuing

NRT. The effect of duration of NRT use on smoking cessation was not examined. If 50% of

those attempting to quit used NRT for only two weeks or less, it should not be surprising to see

that NRT is not effective in the general population. Studies that only assess the effect of NRT use

in the form of use versus non-use, but not taking into account the use duration in quitting

smoking may disguise the effect of NRT in the general population.

13

Furthermore, almost all participants in clinical trials received some type of behavioural support,

or at least clinical visits (getting therapy, follow-up visits and assessment, etc.). The majority of

smokers in the general population do not receive this type of support or reinforcement for

cessation, when attempting to quit. Walsh213 has hypothesized that this personal interaction may

explain the difference in smoking cessation among those who use NRT in clinical trials and those

who use NRT on their own. Kottke et al.214 reported that the number of reinforcing sessions was

related to success six months after intervention in their clinical practice.

The effect found in clinical trials that NRT is largely independent of duration may not be

generalizable to the general population. Perhaps, in the general population, those attempting to

quit need to use NRT for at least six weeks, because of lack of behavioural support or personal

interaction with health professionals. On the other hand, since both clinical trials and one general

population study211 have shown that NRT use for three weeks was associated with smoking

cessation, those attempting to quit may only need to use NRT for three weeks to help them quit

smoking. Only a recent study68 by Alpert et al. reported that using NRT for >6 weeks had no

effects on preventing relapse in the general population. However, this study did not examine the

effect of nicotine patches and gum separately. According to clinical trials, patches are more

effective than gum in smoking cessation. Studies only examining the effect of any NRT (in

combination of patches, gum, and other forms of NRT) may not be sufficient to explain the

effects of NRT in the general population, because the effects of patches and gum (the two

commonly used forms of NRT) may be very different in the general population who generally do

not receive behavioural support as in clinical trials.

14

Chapter 2: Objectives and Hypotheses

2.1 Objectives and Research Questions

The main objectives of this study are to determine whether duration of NRT use is associated

with smoking cessation, and whether there are threshold and ceiling effects of duration of NRT

use. The primary research questions are:

1. Is longer duration of NRT use associated with a higher likelihood of abstinence from

smoking in the general population?

1a. Do smokers who use NRT for a recommended duration (≥ 8 weeks) have a higher likelihood

of abstinence from smoking compared to those who do not use NRT, and compared to those

who use NRT with suboptimal duration (<8 weeks) in the general population?

2. Are there threshold (e.g., NRT use for at least 3 weeks to have an effect) and ceiling (e.g., no

further effect beyond 12 weeks of NRT use) effects of duration of NRT use in quitting

smoking?

3. Is the effect of NRT on smoking cessation compared to not using NRT greater among those

who also use behavioural support than those who do not use behavioural support in the

general population?

15

2.2 Hypotheses

The research hypotheses are listed below.

1. Longer duration of NRT use will be associated with a higher likelihood of abstinence from

smoking in the general population.

1a. Smokers who use NRT for a recommended duration (≥ 8 weeks) will have a higher

likelihood of abstinence from smoking compared to those who do not use NRT, and

compared to those who use NRT for a suboptimal duration (<8 weeks) in the general

population.

2. NRT will have to be used for a certain duration (e.g., using NRT 3 weeks vs. not using

NRT) to have an effect and beyond that duration will have no further effect (e.g., using NRT

>12 weeks vs. using NRT 8-12 weeks) in quitting smoking in the general population.

3. The effect of NRT on smoking cessation compared to not using NRT is greater among those

who also use behavioural support than those who do not use behavioural support in the

general population.

16

Chapter 3: Methods

3.1 Data Source and Study Design

To address these research questions, a series of complex secondary data analyses using the

Ontario Tobacco Survey (OTS) were conducted. The OTS is a regionally-stratified, random-

digit-dial telephone survey. The OTS consists of both cross-sectional survey and a longitudinal

component. The cross-sectional survey component of the OTS consists of a set of six population-

representative telephone surveys of Ontario adults (18 years of age and over), stratified by region

(Eastern, Greater Toronto Area, South Western, and Northern, based on telephone area code) and

smoking status (any smoking in the past six months).

Data collection for the first baseline survey (Cohort 1 of the OTS) began in July 2005; collection

of the final baseline study (Cohort 6) was completed in June 2008. These six cross-sectional

survey samples were paired with a longitudinal component that allowed for repeated follow-up

interviews of the recent smokers (had smoked within the past six months at recruitment). Every 6

months, 750 recent smokers and 500 non-smokers were recruited. Over sampling of smokers

allows detailed analysis of their smoking and cessation behaviours. Recent smokers were

subsequently invited to participate in three follow-up surveys occurring in six-month intervals.

Its longitudinal survey of smokers is a repeated-measures panel study based on 4,572 Ontario

adult recent smokers, who were recruited between July 2005 and June 2008 and were followed

for a minimum of 3 subsequent interviews at six month intervals for up to three years. Survey

data for the OTS were collected by the Survey Research Centre (SRC) at the University of

Waterloo using computer-assisted telephone interview (CATI) technology. The OTS study

focuses on attitudes, behaviours, and beliefs about tobacco, and the factors that influence

smoking cessation and relapse.215 Overall, six cohorts of recent smokers compose the base of the

panel study.

The first cohort was recruited between July and December 2005 and three follow-ups (in six

month intervals) ended by June 2007. The second to sixth cohorts were recruited every six

17

months from between January and June 2006 to between January and June 2008. The last three

follow-ups for the sixth cohort ended by December 2009. The data collection schedule is listed in

the table below (Table 3).

Table 3. Data collection schedule and number of respondents who completed interviews for the longitudinal smokers in the Ontario Tobacco Survey (OTS)

Wave Date Longitudinal

smokers at baseline

Follow-up 1 Follow-up 2 Follow-up 3

1 July-December, 2005 BLC1 (n=749)

2 January-June, 2006 BLC2 (n=752) F1C1 (n=651)

3 July-December, 2006 BLC3 (n=750) F1C2 (n=634) F2C1 (n=590)

4 January-June, 2007 BLC4 (n=752) F1C3 (n=648) F2C2 (n=598) F3C1 (n=575)

5 July-December, 2007 BLC5 (n=752) F1C4 (n=619) F2C3 (n=601) F3C2 (n=543)

6 January-June, 2008 BLC6 (n=749) F1C5 (n=660) F2C4 (n=620) F3C3 (n=552)

7 July-December, 2008 F1C6 (n=623) F2C5 (n=599) F3C4 (n=563)

8 January-June, 2009 F2C6 (n=580) F3C5 (n=572)

9 July-December, 2009 F3C6 (n=545)

Note: BL for baseline, C for cohort, and F for follow-up.

3.2 Criteria for Respondents Included in the Current Study

Respondents in the OTS panel survey were included in this study with the following inclusion

criteria: 1) current smokers at baseline (smoked at least 100 cigarettes lifetime and smoked daily

or occasionally at baseline interview or smoked in the past 30 days) aged 18 or older; and 2)

made at least one serious quit attempt at follow-up (see Appendix 2 for details).

3.3 Outcome Measures

Categorical outcomes of continuous abstinence from smoking for at least one month (short-term

abstinence) and for at least 12 months (long-term abstinence) at final follow-up and the longest

18

quit days ≥ one month and ≥12 months at any follow-up (6, 12, and 18 months of follow-up)

were examined by duration of NRT use (see Appendix 3 for details).

3.4 Measures of NRT Use Duration (Main Independent Variable)

Three forms of NRT duration were determined, including duration of any NRT (including

nicotine patches, gum, inhaler, and lozenges/tablets), nicotine patch (singular form), and nicotine

gum (singular form) use. The longest duration of NRT use at any one follow-up (six months) and

sum of duration of NRT use during all follow-ups for the quitting outcome at final follow-up or

before the longest quitting outcome were examined, and the one fit model best was used.

Duration of NRT use was determined by the answers to the question “over the past 6 months,

how long did you use nicotine patches (gum, inhaler, or lozenge/tablets) to help you quit or stay

smoke free” (see Appendix 3 for details). If respondents did not use any NRT, the duration for

NRT use was coded as zero.

3.5 Potential Confounding Variables and Effect Modifiers

Potential baseline confounding variables assessed included age, sex, education, marital status,

general health, nicotine dependence, past quit history, intention to quit, beliefs about addiction

and quitting, motivation for quitting, social-environmental factors for quitting, and use of quit

aids, and beliefs about quit medications. Potential follow-up confounding variables included use

of bupropion SR and varenicline, use of behavioural support, use of other quit methods (e.g.,

self-help materials and laser therapy), use of other forms of NRT without patches (for the

primary independent variable of patch use duration) and use of other forms of NRT without gum

(for the primary independent variable of gum use duration), use of other tobacco products (e.g.,

cigars and snus), seeing or hearing an ad about stop smoking medication, and number of quit

attempts, as well as time in the study (Table 4). Categories of these potential confounders are

listed in the table; for potential modifiers, the categories are the same as for confounders, unless

otherwise indicated in the table. Social-environmental factors for quitting at follow-up (including

counting on someone for support while quitting; someone making quitting difficult; other

household member smoking; and home smoking restrictions) and health region, in addition to the

19

above potential confounding variables were examined as potential effect modifiers (Table 4)

(details about assessment can be found in the data analysis section). (See Appendix 4 for details).

Table 4. Potential confounders and modifying variables Variable

Category

As a potential confounder

As a potential modifier

Baseline variables Age Continuous Yes Yes

(<30 vs. ≥30; <40 vs. ≥40; and

<50 vs. ≥50) Sex Female vs. male Yes Yes Health region Eastern

Greater Toronto Area South Western Northern

No Yes

Education

<high school High school Some post secondary education College/university graduation (referent group)

Yes Yes ≤high school Post secondary education (referent group)

Marital status Never married Separated/divorced/widowed Married (referent group)

Yes Yes

General health Poor-fair Good-excellent (referent group)

Yes Yes

Tobacco dependence Daily smoking Yes

No (referent group) Yes Yes

Cigarettes/day Continuous Yes Yes (<10 vs. 10+; <20 vs. 20+)

HSI Low (referent group) Medium High

Yes Yes

Past quit history # lifetime quit Continuous Yes Yes (≤2 vs. >2) Tried to quit in last 12 months Yes

No (referent group) Yes Yes

Planned the most recent quit attempt

Yes No (referent group)

Yes Yes

Intention to quit No intention (referent group) Within next 30 days Between next 1 and 6 months Beyond next 6 months Not applicable

Yes Yes

Beliefs about addiction and quitting Self-perceived addiction Very addicted: yes vs. no Yes Yes Self-perceived easiness of quitting Somewhat to very hard: yes vs.

no Yes Yes

Self-perceived confidence of quitting

Fairly to very confident: yes vs. no

Yes Yes

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† Other quit methods including hypnosis, acupuncture, laser therapy, self‐help booklet or video, and a website or a chat group to help quit smoking.

‡ Other forms of NRT without patches for the primary independent variable of patch use duration. § Other forms of NRT without gum for the primary independent variable of gum use duration.

Motivation for quitting Self-perceived quitting benefit Quite a bit to a lot: yes vs. no Yes Yes Quit to reduce disease risk/ improve health

Yes vs. no Yes Yes

Social environmental factors for quitting

Counting on someone for support while quitting

Yes vs. no Yes Yes

Someone making quitting difficult Yes vs. no Yes Yes Other household member smoking Yes vs. no Yes Yes Home smoking restrictions Yes vs. no Yes Yes Workplace smoking ban Yes vs. no Yes Yes Seeing or hearing an ad about stop smoking medication

Yes vs. no Yes Yes

Use of quit aids Ever use of NRT Yes vs. no Yes Yes Ever use of bupropion SR or varenicline

Yes vs. no Yes Yes

Ever use of behavioural support Yes vs. no Yes Yes Ever use of other quit methods† Yes vs. no Yes Yes Beliefs about quit medication Making quitting easier Yes vs. no Yes Yes Medication cost making it difficult to use

Yes vs. no Yes Yes

Hard to get the medication Yes vs. no Yes Yes Concerned about its side effects Yes vs. no Yes Yes Follow-up variables Use of quit aids Bupropion SR or varenicline Yes vs. no Yes Yes Behavioural support Yes vs. no Yes Yes Other quit methods† Yes vs. no Yes Yes NRT no-patches‡ Yes vs. no Yes No NRT no-gum§ Yes vs. no Yes No Use of other tobacco products Yes vs. no Yes Yes # quit attempts Continuous Yes Yes (≤2 vs. >2) Follow-up time Continuous Yes No Social environmental factors for quitting

Seeing or hearing an ad about stop smoking medication

Yes vs. no Yes Yes

Counting on someone for support while quitting

Yes vs. no No Yes

Someone making quitting difficult Yes vs. no No Yes Other household member smoking Yes vs. no No Yes Home smoking restrictions Yes vs. no No Yes Workplace smoking ban Yes, not applicable vs. no Yes Yes

21

The variables listed here (age, gender, education, marital status, nicotine dependence, social

support and other quit aids) have been shown to be associated with smoking cessation.205, 216-219

These factors may be component causes of smoking cessation. To better understand the effect of

NRT use on smoking cessation, these variables were treated as potential effect modifiers. Thus

potential targeted guidelines for NRT use (e.g., older smokers with longer duration of NRT use)

might be recommended.

Research has found that quit rate for nicotine patches versus placebo was higher among men

(OR=2.2) than women (OR=1.61), with an interaction odds ratio of 1.40 (95% CI = 1.02-1.93, p

= .04). There are several possible explanations for sex differences in NRT efficacy, including

variability in rates of compliance,207 withdrawal symptoms, adverse effects,168 and sensitivity to

non-nicotine factors, such as smoking cues between men and women.220 Variability in

phenotypic factors related to smoking behaviour, such as rate of nicotine metabolism, may also

underlie sex differences in response to NRT.221

Older people may have poor health and are more likely to quit smoking. People with higher

education are generally more likely to quit than those with lower education, due to their

knowledge and access to the resources. Married smokers may get support and/or pressure from

their partners for quitting, and thus are more likely to quit than single smokers. Smokers with

high nicotine dependence may find NRT more useful in coping with withdrawal symptoms than

those with low nicotine dependence, and thus are more likely to quit smoking with NRT than

those with low nicotine dependence. These factors (age, education, marital status, etc.) may also

have different effects on the association between NRT use duration and smoking cessation by

their different levels, the same as the difference between men and women (i.e., variations in

rates of compliance, withdrawal symptoms, adverse effects, and sensitivity to no-nicotine

factors, e.g., seeing other people smoking). Therefore, these factors were treated as potential

modifiers and assessed in this study.

22

3.6 Data Analysis

3.6.1 Descriptive Analysis

Mean (SD), median, min-max of duration of abstinence from smoking and NRT use, categorical

abstinence (≥ 1 month and ≥ 12 months) and categorical NRT duration (not using NRT, NRT use

<8 weeks, and NRT use ≥ 8weeks) were described by socio-demographic characteristics (age,

sex, education, and marital status), smoking related variables (daily smoking, cigarettes per day

smoked, and heaviness of smoking index, HSI), and other variables (e.g., self-perceived general

health, addiction, confidence of quitting, etc.).

Patterns of quit attempts and NRT use over time were reported. The proportions of no quit

attempt, one quit attempt, two quit attempts or three quit attempts at all three follow-ups, as well

not using NRT, using NRT at one follow-up, two follow-ups, or all three follow-ups, were

described.

3.6.2 Analyses of Associations

a) Associations between NRT Quit Aid Use Duration and Quitting Outcomes

The short-term (continuous abstinence for at least 1 month) and long-term (continuous

abstinence for at least 12 months) quitting outcomes were examined by the duration of NRT use

(as well as patch and gum use, separately). The duration of NRT use were categorized as 1) not

using NRT, NRT use <8 weeks, and NRT use≥ 8 weeks; and 2) not using NRT, NRT use for <4,

≥4-<8, ≥8-<12, ≥12-<16, and 16+ weeks. Poisson model analyses with robust standard errors

were used to examine the effect of NRT duration on categorical abstinence outcomes so to deal

with potential overdispersion issues. Using Poisson models with robust standard errors (GEE

approach) for the parameter estimates is recommended by Cameron and Trivedi222 to control for

mild violation of the distribution assumption that the variance equals the mean. Relative risk

(RR), 95% CIs and p values were reported.

23

The mathematical equations for rate ratio via Poisson regression model are listed below.

g[E(Y| β, x)] = β0 + β1X1 + … βpXp

where:

P(Y| β,x) = !

μ is the rate,

and g is called “the link function”.223

A more general form is:

Loge(Y) = β0 + β1X1 + … βpXp

where:

Y is the binary outcome,

β0 is the intercept,

β1, β2 … are the coefficients for covariates

X1, X2 … are the covariates

The relative risk (RR) is then given by exp(βi). This model expresses the log outcome rate as a

linear function of a set of predictors.

Because models for the association between the quitting outcome and use duration of NRT quit

aids with different categories (e.g., three groups vs. four groups) were not nested, model fit

cannot be tested using the normal likelihood ratio test. A quasi-log-likelihood under the

independence model information criterion (QIC) statistic, equivalent to Akaike Information

Criterion (AIC), has been recommended for non-nested model selection with GEE estimation.224

The QIC method has been used by other studies in model selection.225, 226 The QIC method was

used in my study to choose groups for use duration of NRT quit aids. For example, if QIC was

24

2226.18 for NRT use duration with three groups (i.e., non-use, use <8 weeks, and use ≥8 weeks),

2220.56 for NRT use duration with four groups (i.e., non-use, use <4 weeks, use ≥4 - <8 weeks,

and use ≥8 weeks), and 2219.78 for NRT use duration with six groups (i.e., non-use, use <4

weeks, use ≥4 - <8 weeks, use ≥8 - <12 weeks, use ≥12 - <16, and use ≥16 weeks), the best fit

model chosen for analysis would be the model with four groups for use duration of NRT quit

aids, as this model had a smaller value than the model with three groups (the difference in QIC

>2) and equivalent inference to the model with six groups, but the model with four groups was a

more parsimonious model compared to the model with six groups.

b) Testing for Confounders and Effect Modifiers

Using Rothman’s and Greenland’s method,227 confounding variables were identified as those

variables that were associated with both the primary independent variable(s) and the outcome

variable(s) (i.e., a predictor for the quitting outcome among the group not using quit aids) (p

value for cross group comparison ≤0.2, using Mantel-Haenszel test).

Once confounding variables were identified, effect modification was examined in the adjusted

analysis controlling for all confounders. Following Kleinbaum’s strategies,228 first, all potential

modifying variables and their interaction terms, in addition to the primary independent variables

and all confounders, were included in one multivariable model. Second, the multivariable

regression model included only modifying variables with significant interaction terms (p<0.05),

in addition to the primary independent variables and all confounders. This process was repeated

until all modifying variables had significant interaction terms.

Because the primary independent variable had two dummy variables, there were two or more

interaction terms for each individual modifying variable. Thus, the overall statistical significance

test of the conditional (modification) relationship was conducted by the likelihood ratio test for

Poisson regression (for binary quitting outcome) without robust variance estimation. Two models

were used to assess the overall significance of the effect modification. Model one contained the

primary independent variables, all confounders, and all modifying variables with significant

25

interaction terms, but the variables for the interaction terms were not included in the model.

Model two contained the variables for the interaction terms for all significant modifying

variables, in addition to the variables in Model one.

For the binary outcomes (continuous cessation ≥ 1 month and ≥ 12 months), the log-likelihood

ratio test was used to assess the additive interaction effect using a Poisson regression model

(using SAS “proc genmod” with options “dist = Poisson” and “link = identity”),229 while in the

normal Poisson regression assessing the association between use duration of NRT quit aids and

quitting outcomes, the options “dist=Poisson” and “link=log” were used.

If the likelihood ratio test showed that the variable was a significant modifying variable ,

subgroup analysis as described by Aneshensel230 was applied to simplify the interpretation (e.g.,

the association between using NRT ≥8 weeks and not using NRT among those who never used

NRT before or among those who used NRT before).

Odds ratios (ORs) are usually used to approximate relative risks (RRs) when the outcome is rare.

ORs will overestimate the RRs as outcomes become more common, which is the case in this

study (the smoking cessation rate is common especially for short-term cessation). Substituting

ORs for RRs in assessing additive interaction may result in misleading conclusions.231, 232 Some

authors have called this “distributional interaction” in that there is an additive interaction when

using ORs but no additive interaction when using RRs in the same data of the same study.231

Thus, in this study, I used Poisson regression instead of logistic regression to conduct all

analyses for the categorical outcomes.

c) Handling Collinearity

Collinearity between confounders might exist in this study. Collinearity can change parameter

estimates, increase standard errors, and reduce the power to detect reliable effects of correlated

variables in multivariable regression analysis. However, collinearity affects only those

26

independent variables highly correlated with other independent variables, but does not affect

other independent variables in the model nor any summary or fit statistics (e.g., R², AIC, or BIC

values).233

Multicollinearity between the primary independent variable (e.g., NRT use duration) and all

potential confounders and effect modifiers listed in section 3.5 were assessed by using a linear

regression that treated NRT use duration and the potential correlated variables as independent

variables and quit days as the dependent variable. Tolerance (1 – R2), variance inflation factor

(VIF = 1/tolerance), and condition index of collinearity diagnostics were calculated for the

potential correlated variables. It was found that VIFs for all variables were <2.5 (except for

intention to quit: between 2.0 and 3.9), but the largest condition index of collinearity diagnostics

for all variables was <2.9 for NRT, patch, and gum use duration. This meant that there was no

important multicollinearity among all independent variables.

Although there is no formal cut-off value to use with VIF for determining presence of

multicollinearity, the rule of 4 or 10 has appeared in the literature to indicate multicollinearity in

linear regression.234 In non-linear regression such as logistic regression, values of VIF above 2.5

may be a cause for concern.235 If VIF for the correlated variables is greater than 2.5, this variable

would need to be centered to avoid collinearity issues. However, it should be noted that values of

VIF of 10, 20, 40, or even higher do not, by themselves, discount the results of regression

analyses, since other factors (such as correlation of the dependent variable to the independent

variables in the model, sample size, and the test for the statistical significance) can reduce the

variance of the regression coefficients far more than VIF inflates these estimates even when VIF

is 10, 20, 40, or more.234 Importantly, “if an investigator is only interested in whether a given

coefficient is significantly positive, and is able, even in the presence of collinearity, to accept that

hypothesis on the basis of the relevant t-test, then collinearity has caused no problem.” (page

116)236

27

d) Data Weighting

Sampling probability weights were produced for baseline respondents. Weights were calculated

for each wave of data collection and according to the sample characteristics and completion rates

for each wave, respectively. For the purposes of the combined baseline dataset, all weights were

recalibrated to sum to the 2006 census population based on age, sex, and health region. In the

analysis, modification analysis stratified by age, sex, and health region was conducted,

respectively. The difference between weighted and un-weighted analyses would be eliminated by

stratification analyses by age, sex and health region. Thus, in the association analysis section,

weighted analysis was not conducted.

3.7 Statistical Power

Statistical power was conducted for both short- and long-term quitting outcomes. The power was

conducted for those who made at least one serious quit attempt during follow-up for the current

study. It should be noted that all statistical power was estimated without taking into account

confounding effects.

Two time periods for outcomes were used: 1) outcome at follow-up three (final follow-up in this

study, approximately 18 months of follow-up); and 2) quitting outcome at any follow-up based

on the longest quit days. The power was conducted by comparing groups between not using NRT

(patches or gum) and using NRT (patches or gum) <8 weeks (power 1), between not using NRT

(patches or gum) and using NRT (patches or gum) ≥8 weeks (power 2), and between using NRT

(patches or gum) <8 weeks and using NRT (patches or gum) ≥8 weeks (power 3). Two-sided

tests with alpha = 0.05 were used in power calculation.

For the quitting outcome ≥1 month at the end of 18 months of follow-up, the statistical power

was greater than 0.80 only for the comparison between using NRT <8 weeks and not using NRT,

while those who did not use NRT had a higher proportion of short-term abstinence. The

statistical power was less than 0.80 for all other comparison groups. For the quitting outcome

28

≥12 months at the end of 18 months of follow-up, the statistical power was less than 0.80 for all

comparisons for NRT, patch, and gum use groups.

For quitting outcome ≥1 month at any follow-up, the statistical power was greater than or equal

to 0.80 for all comparison groups, except two: 1) between using patches <8 weeks and not using

patches (power = 0.76); and 2) between using gum ≥8 weeks and not using gum (power = 0.14).

For the quitting outcome ≥12 months at any follow-up, the statistical power was greater than

0.80 only for two comparison groups: 1) between NRT use ≥8 weeks (higher quit rate) and NRT

use <8 weeks; and 2) between patch use ≥8 weeks (higher quit rate) and patch use <8 weeks.

(For details, see Appendix 5: Power Calculation).

3.8 Sensitivity Analysis

Smokers use NRTs in two ways to help reduce harm from smoking: 1) quit smoking and 2)

reduce number of cigarettes smoked per day. In general population studies, the effect of NRT use

is usually examined among those who make a serious quit attempt. This approach may have

misclassified those who tried to quit and used NRTs, but failed to quit, and thus changed their

intention from quitting to reducing. In this case, the effect of NRT would be overestimated. A

sensitivity analysis was conducted to examine if the magnitude of NRT effect would be

attenuated for the groups of respondents who used NRT to quit and those who used NRT for

reducing smoking. Thus, the misclassification of NRT use based on the condition “making a

serious quit attempt” can be examined to some extent. This sensitivity analysis might be able to

assess the effectiveness of NRT use in the general population overall, using NRT either for

quitting or for reducing smoking (assuming reducing smoking would lead to cessation at some

stage).

Outcome measures and NRT use measures were the same as those for the main analysis. Data

analysis procedures were also the same as those for the main analysis. Respondents in the OTS

panel survey were included in this sensitivity analysis if they changed their smoking behaviour

either by reducing the amount they usually smoke or making at least one serious quit attempt

29

during follow-up (for details, see Appendix 10.1: Questions used to identify participants in the

sensitivity analysis).

3.9 Ethics

Ethical approval for the OTS initiative was received from the appropriate Human Subjects

Research Ethics Committees of the Universities of Waterloo and Toronto, including the intention

to complete secondary data analyses on the subject of smoking cessation.

The current study was a secondary data analysis project not involving personally identifiable

data from study respondents who gave explicit consent for this research. The ethical approval for

this dissertation as supervised research was received from the appropriate Human Subjects

Research Ethics Committees of the University of Toronto in March 2011.

30

Chapter 4: My Role in This Project

I initiated this project and conducted the literature review. From the literature review, I

determined the research gaps. To fill these research gaps, I identified the research questions and

conducted all data analysis based on the existing OTS data. My role in this project also included

interpretation of the results, writing of the thesis, and disseminating the findings through

presentations at scientific conferences and future journal articles.

31

Chapter 5: Potential Scholarly Benefits and Public Health Implications

My study would improve on current knowledge in the following ways:

1) Fill the research gap about the effect of duration of NRT use in smoking cessation in the

general population, as described in the proposal (section 4, pages 11-13).

2) In this study, the recall period is six months, which may have less bias than longer recall (life

time or one year). The longitudinal feature of this study may reduce the recall bias further and

the temporal relationship can be established.

3) This study is a population-based survey using a representative sample, which should have less

selection bias than studies using non-representative samples.

4) Some previous studies did not control for behavioural support, which may over-estimate the

effect of NRT use on smoking cessation. In this study, the effect of behavioural support was

controlled for, thus a more accurate effect of NRT use on smoking cessation would be

identified.

5) In addition, modifying effects of age, tobacco dependence, education etc. were estimated,

which might help make recommendations about NRT use for different populations (e.g.,

heavy smokers should use NRT for at least 12 weeks).

Potential public health implications of my study are discussed below. The majority of current

free NRT studies show a positive effect of NRT use. However, all free NRT studies provided

behavioural support. It is not clear how effective NRT would be without behavioural support. If

my study shows that NRT use for the recommended duration results in a higher likelihood of

smoking cessation without behavioural support including quitline support, NRT products should

be recommended as quit aids in the general population. However, if no matter how long smokers

use NRT, NRT has no effect on smoking cessation in the general population, NRT should not be

recommended in the general population without access to behavioural support. If using nicotine

patches but not gum is found to be associated with smoking cessation, nicotine patches but not

32

gum then should be recommended to be used in the general population of smokers. If this study

finds threshold and ceiling effects, specific guidelines for using NRT appropriately should be

made to improve quitting outcomes in the general population. In addition, if NRT use for certain

duration is effective in some subgroups but not others, targeted recommendations should be

made.

33

Chapter 6: Results

6.1 Descriptive Analysis

6.1.1 Respondents in the OTS Longitudinal Panel Study

At baseline, there were 4,504 self-reported smokers (those who smoked at least one cigarette in

the past six months) among all six cohorts of the OTS longitudinal panel of smokers. There were

4,064 current smokers (those who smoked at least 100 cigarettes lifetime and some during the

past 30 days) among the 4,504 self-reported smokers.

Those who had not smoked 100 cigarettes (n = 146), did not smoke in the past 30 days (n = 291),

or had no information on smoking status (n=3) were excluded from this study.

6.1.2 Respondents and Quit Attempt Patterns, Lost to Follow-up, and Retention Rate

Those who were current smokers at baseline and made at least one serious quit attempt at any

follow-up were eligible respondents in the current study. Among the 4,064 current smokers at

baseline, 1,590 made at least one serious attempt to quit smoking at follow-ups one, two, and/or

three and were eligible for the analysis of short-term quitting outcome (having at least six-

months of follow-up) (Figure 1).

At follow-up one, 902 respondents made at least one serious attempt to quit. At follow-up two,

among the 902 respondents who made a serious attempt to quit at follow-up one, 796

respondents were re-interviewed and 106 lost to follow-up, so that the retention rate from follow-

up one to follow-up two was 88% (= 796/902) among the eligible respondents for this study.

Among those who did not make a serious attempt to quit at follow-up one (n=2,566), 352 made a

serious attempt to quit at follow-up two. Among those who were lost to follow-up at follow-up

one (n=596), 60 made a serious attempt to quit at follow-up two. Thus, the eligible sample size at

34

follow-up two was 1,314 (including the 106 lost to follow-up two, but made a serious attempt to

quit at follow-up one).

At the end of 18 months of follow-up, among the 1,314 respondents who made a serious attempt

to quit at follow-ups one and/or two, 1,092 were re-interviewed and 222 lost to follow-up. Thus

the retention rate from follow-ups one and two to follow-up three was 83% (=1092/1314). The

1,314 respondents were eligible for the analysis of long-term quitting outcome (having at least 12

months of follow-up). Among those who were not eligible respondents at follow-ups one and

two, 276 made a serious attempt to quit smoking at follow-up three. Thus the eligible sample size

for all follow-ups for this study was 1,590. The eligible sample with information on all three

follow-ups was 1,239 (80% of the entire eligible sample). Respondents might get lost to follow-

up at follow-up one or two and re-interviewed at follow-up three, or re-interviewed at follow-up

one but lost to follow-ups two and three (Table 5).

Two approaches for data analysis were used: 1) quitting outcome at follow-up three using the

eligible sample with information at baseline and follow-up three, even if respondents had no

information at follow-ups one and two (n=1,368) (the sample for loss to follow-up three was

222); and 2) quitting outcome at any follow-up using the eligible sample with information at

baseline and any one follow-up, including those who had information at follow-up one only but

no information at follow-ups two and three, those who had information at follow-up two only but

no information at follow-ups one and three, and those who had information at follow-up three

only but no information at follow-ups one and two (n=1,590). For this approach, all eligible

respondents were included in data analysis. Thus, no loss to follow-up occurred in this approach.

For the short-term quitting outcome at the end of 18 months of follow-up, the eligible sample

consisted of those who made at least one serious quit attempt at follow-ups one, two, and/or three

and re-interviewed at the end of 18 months of follow-up, assuming that all serious quit attempts

were made at the beginning of each follow-up period. Thus, smokers would have at least six

months of follow-up after making a serious quit attempt. The sample size was 1,368 among the

35

1,590 baseline current smokers (retention rate: 86.0%). For the long-term quitting outcome at the

end of 18 months of follow-up, the eligible sample was those who made at least one serious quit

attempt at follow-ups one and/or two and were re-interviewed at the end of 18 months of follow-

up. Thus, smokers would have at least 12 months of follow-up after making a serious quit

attempt when assuming that the serious quit attempts were made at the beginning of each follow-

up period. The sample size was 1,092 among the 1,314 baseline current smokers (retention rate:

83%).

Figure 1. Flow diagram for analysis of short-term abstinence on longitudinal respondents who made at least one serious quit attempt at follow-ups one, two, or three and were re-interviewed at follow-up three (having at least six months of follow-up after making a serious quit attempt), OTS longitudinal study 2005-2009

Current smokers at baseline (100+ cigarettes/lifetime

& some in the past 30 days) N = 4,064

Excluded: Non‐current smokers at baseline 1. < 100 cigarettes/lifetime (n = 146) 2. Former smokers (not smoked in the past

30 days; n = 291) 3. Smoking status not known (n = 3)

Those who made a serious attempt to quit at follow‐ups one, two, or three

Total N = 1,590

Those who were re‐interviewed at the end of 18 months of follow‐up

Total N = 1,368

Lost to follow‐up at the end of 18 months N = 222 (retention rate†: 86%)

Excluded: Did not make a serious quit attempt at follow‐ups one, two, or three (n = 2,474)

† Reten on rate was calculated as number of lost to follow‐up divided by the number of those

who made a serious attempt to quit at follow‐up [i.e., (1590‐222)/1590 = 86%]

Baseline recent smokers (At least one cigarette in the past 6 months)

(Complete data) N = 4504

36

Figure 2. Flow diagram for analysis of long-term abstinence on longitudinal respondents who made at least one serious quit attempt at follow-ups one or two and were re-interviewed at follow-up three (having at least 12 months of follow-up after making a serious quit attempt), OTS longitudinal study 2005-2009



Excluded: Non‐current smokers at baseline 1. < 100 cigarettes/lifetime (n = 146) 2. Former smokers (not smoked in the past

30 days; n = 291) 3. Smoking status not known (n = 3)

Those who made a serious attempt to quit at follow‐ups one or two

Total N = 1,314


Total N = 1,092

Lost to follow‐up at the end of 18 months N = 222(retention rate†: 83%)

Excluded:

Did not make a serious quit attempt at

follow‐ups one or two (n = 2,750)


who made a serious attempt to quit at follow‐ups one or two [i.e., (1314‐222)/1314=83%].

Baseline recent smokers (At least one cigarette in the past 6 months)

(Complete data) N = 4504

37

Table 5. Respondents and their serious quit attempt patterns at follow-up, OTS longitudinal study 2005-2009

Pattern

Baseline (current smokers)

FU1† (quit

attempt‡)

FU2† (quit

attempt‡)

FU3† (quit

attempt‡)

Sample size

Sample

for analysis§

Quit attempt ‡ at FU1, FU2 and FU3 Yes Yes Yes Yes 183 Yes Quit attempt at FU1 and FU2, no quit attempt at FU3 Yes Yes Yes No 142 Yes Quit attempt at FU1 and FU2, lost at FU3 Yes Yes Yes Lost 46 Yes Quit attempt at FU1, no quit attempt at FU2, quit attempt at FU3

Yes Yes No Yes 109 Yes

Quit attempt at FU1, no quit attempt at FU2 and FU3 Yes Yes No No 266 Yes Quit attempt at FU1, not quit attempt at FU2, lost at FU3 Yes Yes No Lost 50 Yes Quit attempt at FU1, lost at FU2, quit attempt at FU3 Yes Yes Lost Yes 20 Yes Quit attempt at FU1, lost at FU2, no quit attempt at FU3 Yes Yes Lost No 20 Yes Quit attempt at FU1, lost at FU2 and FU3 Yes Yes Lost Lost 66 Yes No quit attempt at FU1, quit attempt at FU2 and FU3 Yes No Yes Yes 123 Yes No quit attempt at FU1, quit attempt at FU2, no quit attempt at FU3

Yes No Yes No 191 Yes

No quit attempt at FU1, quit attempt at FU2, lost at FU3 Yes No Yes Lost 38 Yes No quit attempt at FU1 and FU2, quit attempt at FU3 Yes No No Yes 225 Yes No quit attempt at FU1, FU2 and FU3 Yes No No No 1513 No No quit attempt at FU1 and FU2, lost at FU3 Yes No No Lost 182 No No quit attempt at FU1, lost at FU2, quit attempt at FU3 Yes No Lost Yes 28 Yes No quit attempt at FU1, lost at FU2, No quit attempt at FU3 Yes No Lost No 78 No No quit attempt at FU1, lost at FU2 and FU3 Yes No Lost Lost 188 No Lost at FU1, quit attempt at FU2 and FU3 Yes Lost Yes Yes 18 Yes Lost at FU1, quit attempt at FU2, no quit attempt at FU3 Yes Lost Yes No 20 Yes Lost at FU1, quit attempt at FU2, lost at FU3 Yes Lost Yes Lost 22 Yes Lost at FU1, no quit attempt at FU2, quit attempt at FU3 Yes Lost No Yes 21 Yes Lost at FU1, no quit attempt at FU2 and FU3 Yes Lost No No 62 No Lost at FU1, no quit attempt at FU2, lost at FU3 Yes Lost No Lost 35 No Lost at FU1 and FU2, quit attempt at FU3 Yes Lost Lost Yes 2 Yes Lost at FU1 and FU2, no quit attempt at FU3 Yes Lost Lost No 6 No Lost at FU1, FU2 and FU3 Yes Lost Lost Lost 410 No Overall sample 4064 Eligible sample for analysis¶ 1590

38

Eligible sample with information at all three follow‐ups (% of eligible sample) 1239 (77.9%) Eligible sample with information at FU1 and FU2 but lost at FU3 (% of eligible sample) 134 (8.4%) Eligible sample with information at FU1 and FU3 but lost at FU2 (% of eligible sample) 68 (4.3%) Eligible sample with information at FU2 and FU3 but lost at FU1 (% of eligible sample) 59 (3.7%) Eligible sample with information at FU1 but lost at FU2 and FU3 (% of eligible sample) 66 (4.2%) Eligible sample with information at FU2 but lost at FU1 and FU3 (% of eligible sample) 22 (1.4%) Eligible sample with information at FU3 but lost at FU1 and FU2 (% of eligible sample) 2 (0.1%) Eligible sample for short‐term quitting outcome at the end of 18 months of follow‐up 1368 Eligible sample for long‐term quitting outcome at the end of 18 months of follow‐up 1092 Ineligible sample excluded from analysis with regard to short‐term quit outcome at the end of 18 months of follow‐up

2474

Ineligible sample excluded from analysis with regard to long‐term quit outcome at the end of 18 months of follow‐up

2750

† FU, follow‐up. ‡ Quit attempt, making a serious attempt to quit smoking at follow‐up. § Sample included in any one of the analyses (for short‐term or long‐term abstinence at the end of 18 months of follow‐up or at any period of follow‐up) ¶ Baseline current smokers who made a serious attempt to quit smoking at follow‐up; the sample for analysis of short‐term quitting outcome at any period of follow‐up.

39

Among the 1,368 smokers who were eligible for the short-term quitting outcome at the end of 18

months, 1,239 (90.6%) had complete data at baseline and all three follow-ups; 68 (5.0%) had

data at baseline, follow-ups one and three, but missing at follow-up two; 59 (4.3%) had data at

baseline and follow-ups two and three, but missing at follow-up one; and 2 (0.1%) had data at

baseline and follow-up three, but missing at follow-ups two and three. Among the 1,092 smokers

who were eligible for the long-term quitting outcome at the end of 18 months, 1,014 (92.3%) had

complete data at baseline and all three follow-ups; 40 (3.7%) had data at baseline and follow-ups

one and three, but missing at follow-up two; and 38 (3.5%) had data at baseline and follow-ups

two and three, but missing at follow-up one. Overall, less than 10% of the sample had missing

data at some follow-up points, in which 129 (9.4%) smokers had incomplete data for the short-

term quitting outcome and 78 (7.2%) for the long-term quitting outcome at the end of 18 months

of follow-up.

Among the 1,590 smokers who were eligible for the short-term quitting outcome at any period of

follow-up, 1,239 (77.9%) smokers had complete data at baseline and all three follow-ups; 104

(6.5%) had data at baseline and follow-up one, but missing at follow-ups two and three; 96

(6.0%) had data at baseline and follow-ups one and two, but missing at follow-up three; 68

(4.3%) had data at baseline and follow-ups one and three, but missing at follow-up two; 59

(3.7%) had data at baseline and follow-ups two and three, but missing at follow-up one;

22(1.4%) had data at baseline and follow-up two, but missing at follow-ups one and three; and 2

(0.1%) had data at baseline and follow-up three, but missing at follow-ups one and two. Among

the 1,314 smokers who were eligible for the long-term quitting outcome at any period of follow-

up, 1,014 (77.2%) had complete data at baseline and all three follow-ups; 134 (10.2%) had data

at baseline and follow-ups one and two, but missing at follow-up three; 66 (5.0%) had data at

baseline and follow-up one, but missing at follow-ups two and three; 40 (3.0%) had data at

baseline and follow-ups one and three, but missing at follow-up two; 38 had data at baseline and

follow-ups two and three, but missing at follow-up one; and 22 had data at baseline and follow-

up two, but missing at follow-ups one and three; Overall, approximately 23% of the sample for

the short- and long-term quitting outcomes at any period of follow-up had missing data at some

points of follow-up.

40

Smokers who were lost to follow-up would have fewer opportunities to provide complete data.

The serious quit attempts in the current study were assumed to occur at the beginning of each

follow-up so that smokers who made a serious quit attempt at follow-ups one, two, or three

would have at least six months of follow-up after making the serious quit attempt and were

eligible for the short-term quitting outcome at the end of 18 months of follow-up. Similarly,

smokers who made a serious quit attempt at follow-ups one or two would have at least 12

months of follow-up after making the serious quit attempt and were eligible for the long-term

quitting outcome. Smokers might make a serious quit attempt at other times rather than the

beginning of each follow-up. To determine the impact of these potential biases (i.e., smokers

with incomplete data and making the serious quit attempt not at the beginning of the follow-up),

additional analyses using smokers with complete data (having information at baseline and all

three follow-ups) were conducted. For the short-term quitting outcome, smokers (n=1,014) who

made a serious quit attempt at follow-up one or two and had complete data were included in the

analysis. (i.e., having at least six months of follow-up after making a serious quit attempt). For

the long-term quitting outcome, smokers (n=700) who made a serious quit attempt at follow-up

one and had complete data were included in the analysis. (i.e., having at least 12 months of

follow-up after making a serious quit attempt). Results based on these additional analyses

confirmed the findings in my current study (see Appendix 12).

41

6.1.3 Comparison of Those Included in the Analysis and Those Lost to Follow-up

Loss to follow-up occurred for the quitting outcome at follow-up three. Among the 1,590 current

smokers at baseline who made a serious attempt to quit smoking at follow-ups one, two, or three,

222 were lost to follow-up at follow-up three.

In general, those who were lost to follow-up were very similar to those who were included in the

analysis. The major difference was age. Among those who were lost to follow-up, there were

more younger and never married people than those included in the analysis (aged 18-24: 24% vs.

12% and never married: 34% vs. 22%, respectively), and these two variables were correlated

(i.e., younger people were more likely to be never married). On average, those included in the

analysis were five years older than those lost to follow-up. All other demographic characteristics,

smoking-related variables (daily smoking, cigarettes per day smoked, heaviness of smoking

index, , smoking other tobacco products, intention to quit, and lifetime quit attempts), and using

quit aids at baseline were almost identical (the difference in proportion <5%, and p values

>0.05), with one exception: the percentage of those who tried to quit in 12 months prior to

baseline was significantly higher among those who were lost to follow-up (40%) than those who

were included in the analysis (33%) (p <0.05) (Table 6).

It is worth noting that for the quitting outcome at any follow-up, there was no loss to follow-up.

For example, if someone was interviewed at follow-up one but lost to follow-ups at two and

three, this person would be included in the analysis for the quitting outcome at any follow-up

with available information.

42

Table 6. Baseline characteristics of those included and those lost to follow-up three for quitting outcomes at the end of 18 months of follow-up, OTS longitudinal study 2005-2009

Included (n = 1,368)

Lost to follow‐up (n = 222)

Absolute difference

Characteristics n % n % P value

Age (years) Mean (SD)† 43.1 14.3 38.1 15.0 5.0 <0.001 Median (min‐max) 43 18‐88 37 18‐79 6.0 18‐24 166 12.2 52 23.5 11.3% <0.001 25‐39 379 27.9 75 33.9 6.0% 40‐54 517 38.0 62 28.1 9.9% 55‐64 205 15.1 16 7.2 7.9% 65+ 93 6.8 16 7.2 0.4% Sex Female 788 57.6 119 53.6 4.0% 0.264 Education <High school 212 15.7 36 16.5 0.8% 0.884 High school 406 30.1 67 30.7 0.6% Some post‐secondary 161 11.9 22 10.1 1.8% Post‐secondary graduation 570 42.3 93 42.7 0.4% Marital status Never married 295 21.7 75 33.8 12.1% <0.001 Married/common law 751 55.1 98 44.1 11.0% Widowed/separated/ divorced 316 23.2 49 22.1 1.1%

Self‐perceived health Good ‐ Excellent 1068 79.6 163 75.5 4.1% 0.168 Poor – Fair 274 20.4 53 24.5 4.1% Smoking status Daily 1051 76.8 168 75.7 1.1% 0.707 Occasionally 317 23.2 54 24.3 1.1% Cigarettes per day Mean (SD) † 14.3 9.8 14.6 11.2 0.3 0.707 Median (min‐max) 12.1 1‐90 11.7 1.3‐75 0.4 1‐10 cigarettes/day 535 39.1 92 41.4 2.3% 0.625 11‐20 cigarettes/day 546 39.9 81 36.5 3.4% 21+ cigarettes/day: 287 21.0 49 22.1 1.1% Heaviness of smoking index Low 347 30.6 61 33.3 2.7% 0.749 Moderate 458 40.4 70 38.3 2.1% High 329 29.0 52 28.4 0.6% Using other tobacco (e.g., cigar, snus, etc.) 123 10.9 29 15.7 4.8% 0.061 Number of lifetime quit attempts Mean (SD)† 4.3 8.6 3.6 7.3 0.7 0.267 Median (min‐max) 3 0‐200 2 0‐100 1.0

43

Tried to quit in the last 12 months 446 32.6 89 40.1 7.5% 0.029 Intention to quit Within the next 30 days 315 23.0 54 24.3 1.3% 0.570 Within 1‐6 months 453 33.1 78 35.1 2.0% Beyond next 6 months 353 25.8 56 25.2 0.6% No intention to quit 155 11.3 18 8.1 3.2% Not applicable 92 6.5 16 7.2 Ever used NRT‡ 801 58.6 124 55.9 2.7% 0.450 Ever used other pharmaceutical aids§ 403 29.5 63 28.4 1.1% 0.743 Ever used behaviour support†† 207 15.1 32 14.4 0.7% 0.782 Ever used other methods‡‡ 442 32.3 65 29.3 3.0% 0.369

† SD, standard deviation. ‡ NRT, including any use of nicotine patches, gum, inhaler, and lozenges/tablets. § Other pharmaceutical aids including bupropion RS and varenicline. †† Behavioural support including group counselling, specialized addiction counselling, Ontario Quitline,

smokers helpline online, and taking parting in a quit program. ‡‡ Other methods including hypnosis, acupuncture, laser therapy, self‐help booklet or video, and a

website or a chat group to help quit smoking.

6.1.4 Baseline and Follow-up Characteristics of Respondents: Overall

6.1.4.1 Overall sample (un-weighted)

A. Baseline characteristics

a) Demographic characteristics and general health

Among the 1,590 eligible respondents (i.e., baseline current smokers who made a serious attempt

to quit during follow-up), the mean age was 42 years old, while the majority (51%) of

respondents in this sample were middle aged (40-64 years old). There were more females (57%)

than males. More than half (55%) of respondents had some post-secondary education or post-

secondary graduation. The majority of the sample was married (54%), with 23% for never

married and widowed/separated/divorced, respectively. The majority (77%) of respondents

perceived their general health as good to excellent, only 23% as poor to fair (Table 7).

44

b) Nicotine dependence

There were more daily smokers (77%) than occasional smokers (23%) in the sample. On

average, these smokers (both daily and occasional) smoked 14 cigarettes/day. Approximately

39% smoked 1-10 cigarettes/day, 39% smoked 11-20 cigarettes/day, and 21% smoked 21+

cigarettes/day. The proportions for the low, middle, and high level of heaviness of smoking

index (HSI) were 31%, 40% and 29%, respectively. About 10% of respondents also used other

tobacco products (such as cigars, pipes, and snus) (Table 7).

c) Past quit history

On average, respondents in this study made four quit attempts in their lifetime. Approximately

34% of respondents tried to quit in the last 12 months prior to baseline. Just fewer than 20% of

respondents planned their most recent quit attempt (Table 7).

d) Intention to quit and beliefs about addiction and quitting

Almost a quarter (23%) of respondents intended to quit smoking in the next 30 days, 33%

intended to quit smoking within 1-6 months, 26% intended to quit smoking beyond the next 6

months, and 11% had no intention to quit at all at baseline. About 13% had set a firm quit date

for the planned quit attempt. The majority (64%) of respondents perceived that they were very

addicted to cigarette smoking and over 80% felt that it would be hard (somewhat to very hard)

for them to quit. However, around 63% of respondents felt fairly to very confident about quitting

completely if they wanted to (Table 7).

e) Motivational variables for quitting

The majority (82%) of respondents perceived that quitting smoking would give them a lot of

benefits from health or other aspects. Over one-third (37%) reported that the main reason for

them to plan to quit was to reduce disease risk or improve health (Table 7).

45

f) Social-environmental factors for quitting

The majority (82%) of respondents thought that they were able to count on someone to support

quitting; almost half (47%) thought someone would make it more difficult to quit. Over half

(53%) of respondents had home smoking restrictions (no smoking indoors or on the property). A

small proportion (<6%) of respondents reported that other household member(s) smoked. The

majority of respondents (68%) reported seeing or hearing an advertisement about stop smoking

medications such as nicotine patches and gum in past the 30 days prior to baseline (Table 7).

g) Quit aids

Just over half (58%) of respondents ever used NRT products, 29% ever used other

pharmaceutical products (mainly bupropion SR and varenicline), 15% ever used behavioural

support (including group counselling, specialized addiction counselling, the Ontario Quitline,

smokers helpline online, and taking part in a quit program), and 32% ever used other methods

(including hypnosis, acupuncture, laser therapy, self-help booklet or video, and a website or a

chat group). The respondents used these aids individually or in combination with others (Table

7).

In terms of using a combination of quit aids, 29% of respondents never used any quit aids at

baseline, 20% used (ever use) NRT only, 10% used both NRT and other pharmaceutical products

(bupropion SR and varenicline), a small proportion (2%) used both NRT and behavioural

support, 9% used NRT and other methods (e.g., hypnosis, laser therapy and self-help materials),

17% used NRT and other types of quit aids (other pharmaceutical products, behavioural support,

hypnosis, and laser therapy or self-help materials), and 13% used other quit aids without NRT.

The combination use did not mean concurrent use, but ever use of two or more of the quit aids

(Table 7).

46

h) Beliefs about quit medication

The majority (72%) of respondents believed that using quit medications would make quitting

easier, but over half of them (58%) thought that the cost of the medication would make it

difficult to use. Over one-third of respondents (39%) were concerned about the side effects of

quit medications, and a small proportion (9%) of them perceived that the quit medication would

be difficult to get (Table 7).

B. Follow-up characteristics

a) Quitting outcomes

During all three follow-ups (18 month follow-up), respondents made three serious quit attempts

on average; half of them made two serious quit attempts. At the end of 18 months of follow-up,

26% of respondents quit smoking for at least one month, and less than 5% quit smoking for at

least 12 months. Just under half (48%) of respondents quit for at least one month and 5% quit for

at least 12 months based on their longest quit days during any follow-up. Less than 1% of

respondents quit continuously from follow-up one to follow-up three. The mean of the longest

continuous quit days was 79 days and half of them quit less than one month during the 18 month

follow-up (Table 7).

b) Quit aids and using other tobacco products

Among follow-up NRT users, the average NRT use duration ranged from 22 to 29 days and the

median from 9 to 14 days during follow-ups one, two, and three. Only a small percentage (≤4%)

of respondents used NRT for the recommended duration of eight weeks or longer during follow-

up. The majority (75%-79%) of respondents did not use any NRT to quit smoking, and around

two-tenths (19%-22%) used NRT for less than eight weeks during the three follow-ups. Almost

over 60% of respondents did not use any quit aids, around 15% of respondents used NRT only,

8%-10% used both NRT and other quit aids, and another 14% used other quit aids without NRT

at follow-up. The patterns of quit aid use were very similar for the three follow-ups. The

47

proportion of smokers using other tobacco products (e.g., cigar, pipes and snus) was slightly

higher at follow-up than at baseline (Table 7).

The proportion of smokers using two or more NRT products at the same time was 1.4%, 1.3%,

1.3%, and 3.3% among all respondents who made a serious quit attempt, and 5.9%, 6.0%, 6.5%,

and 8.4% among NRT users, at follow-ups one, two, three, and all follow-ups, respectively. The

proportion of smokers using NRT and other pharmaceutical medications (bupropion SR and

varenicline) was 1.0%, 0.8%, 0.6%, and 1.8% among all respondents who made a serious quit

attempt and 4.3%, 3.3%, 2.9%, and 4.4% among NRT users, at follow-ups one, two, three, and

all follow-ups, respectively. The proportion of smokers using NRT and behavioural support (e.g.,

counselling and quit helpline) was 0.2%, 0.4%, 0.3%, and 0.9% among all respondents who

made a serious quit attempt and 0.8%, 2.1%, 1.6%, and 2.1% among NRT users, at follow-ups

one, two, three, and all follow-ups, respectively (Table 7).

The proportion of smokers using different types of NRT was 15.4% for patches, 10.6% for gum,

2.5% for inhaler, and 0.7% for lozenge at follow-up one; 12.7% for patches, 10.4% for gum,

2.4% for inhaler, and 1.0% for lozenge at follow-up two; and 12.6% for patches, 11.1% for gum,

2.3% for inhaler, and 0.8% for lozenge at follow-up three (Table 7). Thus, the most common

types of NRT used by the Ontario smokers when attempting to quit were patches and gum.

c) Social-environmental factors

The proportion of “being able to count on someone to support quitting” slightly increased from

82% at baseline to 85% at follow-up, and the proportions of “someone making quitting difficult”,

other household member smoking, home smoking restrictions, and seeing or hearing an ad about

stop smoking medications increased greatly from 47%, 6%, 53%, and 68% at baseline to 57%,

18%, 71%, and 87% at follow-up, respectively (Table 7).

48

d) Follow-up time

At follow-up one, the average time in the study was 186 days (median = 182 days), with a

minimum time of 166 days and a maximum of 311 days. At follow-up two, the average time in

the study was 372 days (median = 368 days), with a minimum time of 346 days and a maximum

of 502 days. At follow-up three, the average time in the study was 557 days (median = 553

days), with a minimum time of 517 days and a maximum of 697 days (Table 7).

6.1.4.2 Comparison of un-weighted and weighted samples

Weighted and un-weighted samples were very similar in almost all aspects. The major

differences included that the weighted sample was slightly younger than the un-weighted one

(39.3 vs. 42.4); there were fewer females and widowed/separated/divorced people in the

weighted sample (47% and 15%, respectively) than the un-weighted (57% and 23%,

respectively); there were higher proportions of low level of HSI and home smoking restrictions

in the weighted sample (39% and 64%, respectively) than un-weighted sample (31% and 53%,

respectively), and the median day of NRT use at follow-up three was shorter in the weighted

sample (9.1 days) than the un-weighted sample (14 days). The differences for all other variables

were all <7% for percentages, and ≤3.1 for mean and median values (Table 7).

49

Table 7. Characteristics of respondents who made serious quit attempts at follow-up: un-weighted and weighted, OTS longitudinal study 2005-2009

Un‐weighted (N = 1,590)

Weighted (N = 733,461) Absolute

difference Timing Characteristics n % %

Baseline Socio‐demographic characteristics

Age (years) Mean (SD or SE)† 42.4 14.5 39.3 0.5 3.1 Median (min‐max) 43 18‐88 38.3 18‐88 4.7 18‐24 218 13.8 20.5 6.7% 25‐39 454 28.7 31.4 2.7% 40‐54 579 36.6 32.9 3.7% 55‐64 221 14.0 8.6 5.4% 65+ 109 6.9 6.6 0.3% Sex Female 907 57.0 47.1 9.9% Education <High school 248 15.8 12.5 3.3% High school 473 30.2 30.5 0.3% Some post‐secondary 183 11.7 11.6 0.1% Post‐secondary graduation 663 42.3 45.4 3.1% Marital status Never married 370 23.4 28.7 5.3% Married/common law 849 53.6 56.7 3.1% Widowed/separated/divorced 365 23.0 14.6 8.4% General health Self‐perceived health Good – Excellent 1231 77.4 79.2 1.8% Poor – Fair 359 22.6 20.8 1.8% Nicotine dependence Smoking status Daily 1219 76.7 71.7 5.0% Occasionally 371 23.3 28.3 5.0% Cigarettes per day Mean (SD or SE)† 14.3 10.0 13.2 0.3 1.1 Median (min‐max) 12 1‐90 11.0 1‐90 1.0 1‐10 cigarettes/day 627 39.4 45.1 5.7% 11‐20 cigarettes/day 627 39.4 36.8 2.6% 21+ cigarettes/day 336 21.1 18.1 3.0% Heaviness of smoking index Low 408 31.0 38.9 7.9% Moderate 528 40.1 35.2 4.9% High 381 28.9 25.8 3.1% Using other tobacco (e.g., cigar,

snus) 152 9.6 11.6 2.0%

50

Past quit history # of lifetime quit attempts Mean ((SD or SE)† 4.0 8.3 3.7 0.2 0.3 Median (min‐max) 2 0‐200 1.7 0‐200 0.3 Tried to quit in the last 12 months 535 33.7 33.8 0.1% Planned the most recent quit

attempt 310 19.5 15.8 3.7% Intention to quit Intention to quit Within the next 30 days 369 23.2 22.4 0.8% Within 1‐6 months 531 33.4 31.7 1.7% Beyond next 6 months 409 25.7 28.3 2.6% No intention to quit 173 10.9 9.7 1.2% Not applicable 108 6.8 7.9 1.1% A firm date for the planned quit

attempt

208

13.1

13.4

0.3% Beliefs about addiction and

quitting Self‐perceived addiction Not at all to somewhat addicted 579 36.4 43.3 6.9% Very addicted 1011 63.6 56.7 6.9% Self‐perceived easiness to quit Somewhat to very easy 289 18.2 21.8 3.6% Somewhat to very hard 1301 81.8 78.2 3.6% Self‐perceived confidence to quit

completely Fairly to very confident 999 62.8 65.3 2.5% Not very to not at all confident 591 37.2 34.7 2.5% Motivational variables for

quitting Perceived benefit from quitting Quite a lot to a lot 1302 81.9 79.9 2.0% Not at all to little 288 18.1 20.1 2.0% Main reason for planning to quit To reduce disease risk or

improve health

594

37.4

34.0

3.4% Social‐environmental factors for

quitting Able to count on someone to

support quitting

1295

81.5

83.9

2.4% Someone making quitting difficult 743 46.7 48.9 2.2% Other household member(s)

smoking 87

5.5

5.5

0.0%

No indoor smoking at home 846 53.2 64.0 10.8% Seeing or hearing an ad about

stop smoking medication such as nicotine patch and gum

1084

68.2

67.3

0.9%

51

Quit aids Ever use of quit aid patterns Ever used NRT‡ to quit smoking 925 58.2 52.2 6.0% Ever used other pharmaceutical

aids§

466

29.3

25.0

4.3% Ever used behaviour support¶ 239 15.0 13.3 1.7% Ever used other methods†† 507 31.9 27.6 4.3% Ever use of NRT‡ in combina on

with others None 467 29.4 34.8 5.4% NRT‡ only 322 20.3 20.7 0.4% NRT‡ and other pharmaceu cal

aids§

156

9.8

8.7

1.1% NRT‡ and behavioural support¶ 37 2.3 1.7 0.6% NRT‡ and other quit methods†† 143 9.0 7.8 1.2% NRT‡ and two or more other

quit aids

267

16.8

13.3

3.5% All other quit aids†††without

NRT

198

12.5

13.0

0.5% Beliefs about quit medications Using medications making

quitting easier

1150

72.3

71.0

1.3% Difficult to use medications due

to the cost

929

58.4

55.6

3.0% Hard to get quit medications 150 9.4 10.4 1.0% Concerning the side effects 620 39.0 40.6 1.6%

Follow ‐up

Quitting outcomes # of serious quit attempts at 18 month FU

Mean (SD or SE)† 2.9 3.3 2.8 0.1 0.1 Median (min‐max) 2 1‐41 1.4 1‐41 0.6 Quit ≥ 1 month at follow‐up 3 353 25.8 26.8 1.0% Quit ≥ 12 months at follow‐up 3 64 4.7 4.9 0.2% Quit ≥ 1 month at any follow‐up 768 48.3 48.5 0.2% Quit ≥ 12 months at any follow‐up 80 5.0 5.5 0.5% Continuous abstinence from

baseline to FU1 27 1.8 2.9 1.1% Continuous abstinence from

baseline to FU2 15

1.0

1.5

0.5%

Continuous abstinence from baseline to FU3

12

0.9

1.4

0.5%

Longest quit days during any follow‐up

Mean (SD or SE)† 78.7 117.3 81.8 5.1 3.1

Median (min‐max) 28 0‐666 27.0 0‐666

1.0

52

Quit aids NRT‡ use dura on at follow‐up 1 Mean (SD or SE)†days among

users 22.2

33.9

21.6

2.5

0.6

Median (min‐max) days among users

9

1‐183

8.2

1‐183

0.8

Not using NRT 1131 75.1 78.0 2.9% NRT‡ use <8 weeks 332 22.0 19.6 2.4% NRT‡ use ≥8 weeks 44 2.9 2.4 0.5% All quit aid use patterns at follow‐

up 1 None 898 59.6 62.9 3.3% NRT‡ only 241 16.0 14.5 1.5% NRT‡ and other pharmaceu cal

aids§ 23

1.5

1.5

0.0%

NRT‡ and behavioural support¶ 30 2.0 1.9 0.1% NRT‡ and other quit methods†† 49 3.3 2.4 0.9% NRT‡ and two or more other

quit aids‡‡ 42

2.8

2.1

0.7%

All other quit aids‡‡ without NRT

224

14.9

14.6

0.3%

Patch use 232 15.4 12.5 2.9% Gum use 159 10.6 10.0 0.6% Inhaler use 37 2.5 2.1 0.45 Lozenge use 11 0.7 0.6 0.1% Use quit aids at the same time Using two or more forms of NRT 22 1.4 1.0 0.4% Using NRT and other

pharmaceutical aids§

16

1.0

0.8

0.2% Using NRT and behavioural

support¶

3

0.2

0.3

0.1% NRT‡ use dura on at follow‐up 2 Mean (SD or SE)†days among

users

29.2

44.1

26.6 3.1

2.6


10

0‐240

9.2

0‐240

0.8

Not using NRT 1123 77.2 79.1 1.9% NRT‡ use <8 weeks 273 18.8 17.9 0.9% NRT‡ use ≥8 weeks 58 4.0 3.0 1.0% All quit aid use patterns at follow‐


aids§ 20

1.4

0.9

0.5%

NRT‡ and behavioural support¶ 22 1.5 1.4 0.1% NRT‡ and other quit methods†† 34 2.3 2.0 0.3% NRT‡ and two or more other 37 2.5 2.2 0.3%

53

quit aids‡‡ All other quit aids‡‡ without

NRT

207

14.2

13.0

1.2% Patch use 185 12.7 10.5 2.2% Gum use 151 10.4 10.0 0.4% Inhaler use 35 2.4 2.3 0.1% Lozenge use 15 1.0 0.8 0.2% Using quit aids at the same time Using two or more forms of NRT 20 1.3 0.8 0.5% Using NRT and other


11

0.8

0.6


support¶

7

0.4

0.4

0.0% NRT‡ use dura on at follow‐up 3 Mean (SD or SE)† days among

users 28.5

46.2

25.7

3.1

2.8


14

1‐360

9.1

1‐360

4.9

Not using NRT 1058 77.3 79.2 1.9% Using NRT‡ <8 weeks 258 18.9 17.9 1.0% Using NRT‡ ≥8 weeks 52 3.8 2.9 1.9% All quit aid use patterns at follow‐


aids§ 28

2.1

1.4

0.7%

NRT‡ and behavioural support¶ 19 1.4 1.1 0.3% NRT‡ and other quit methods†† 27 2.0 1.6 0.4% NRT‡ and two or more other

quit aids‡‡ 39

2.9

2.7

0.2%

All other quit aids‡‡ without NRT

192

14.0

12.6

1.4%

Patch use 172 12.6 10.9 1.7% Gum use 152 11.1 10.4 0.7% Inhaler use 32 2.3 2.4 0.1% Lozenge use 11 0.8 0.6 0.2% Using quit aids at the same time Using two or more forms of NRT 20 1.3 1.0 0.3% Using NRT and other


9

0.6

0.6


support¶

5

0.3

0.4

0.1% Times of NRT use during all three

follow‐ups None 933 58.7 62.9 4.2% At least at one follow‐up 378 23.8 21.0 2.8% At least at two follow‐ups 198 12.5 11.9 0.6%

54

At all three follow‐ups 81 5.1 4.1 1.0% NRT use duration during 18 month

follow‐up Mean ((SD or SE)† days among

users 40.9

71.1

37.8

3.8

3.1

Median (mix‐max) days among users

15.0

1‐720

13.8

1‐720

1.2

Using other tobacco 238.0 15.0 18.2 3.2% Social‐environmental factors for


support quitting

1344

84.5

85.6

1.1% Someone making quitting difficult 904 56.9 58.0 1.1% Other household member(s)

smoking 293 18.4 17.5 0.9% No indoor smoking at home 1135 71.4 77.8 6.4% Seeing or hearing an ad about

stop smoking medication such as nicotine patch and gum 1380 86.8 86.4 0.2%

Follow‐up time Time in the study at follow‐up 1 Mean (SD)† days 185.6 12.3 Median (min‐max) days 182.0 166‐311 Time in the study at follow‐up 2 Mean (SD)† days 372.4 17.0 Median (min‐max) days 368.0 346‐502 Time in the study at follow‐up 3 Mean (SD)† days 557.4 21.0 Median (min‐max) days 553.0 517‐697

† SD, standard deviation for un‐weighted sample; SE, standard error for weighted sample. ‡ NRT, including any use of nicotine patches, gum, inhaler, and lozenges/tablets. § Other pharmaceutical aids including bupropion SR and varenicline. ¶ Behavioural support including group counselling, specialized addiction counselling, Ontario Quitline,

smokers helpline online, and taking parting in a quit program. †† Other methods including hypnosis, acupuncture, laser therapy, self‐help booklet or video, and a

website or a chat group to help quit smoking. ‡‡ Other quit aids, including other pharmaceu cal aids (e.g., bupropion SR or varenicline), behavioural

support (e.g., counselling), and other methods (e.g., hypnosis and laser therapy).

55

6.1.5 Baseline and Follow-up Characteristics of Respondents: By NRT Use Duration

Baseline and follow-up characteristics of respondents (i.e., current smokers at baseline who

made a serious attempt to quit smoking during follow-up) were compared by NRT use duration

at the 18 month follow-up, including not using NRT, using NRT <8 weeks, and using NRT ≥8

weeks. Overall, almost 60% of respondents did not use NRT at any follow-up, 34% used NRT

<8 weeks, and less than 8% used NRT ≥8 weeks.

A. Comparison between non-NRT users and NRT users

NRT users were generally older than non-NRT users, especially those who used NRT ≥8 weeks.

There were more females but fewer never married people among NRT users than non-NRT

users. More non-NRT users perceived their health as good-excellent than NRT users. There was

no difference in education between NRT and non-NRT users (Table 8).

There were more daily and heavy smokers (smoked 20+ cigarettes/day) with a high level of HSI

among NRT users than non-NRT users, but there was no difference in using other tobacco

products (e.g., cigars and snus). The number of lifetime quit attempts was slightly higher among

NRT users than non-NRT users. More non-NRT users tried to quit in the past 12 months prior to

baseline than NRT users, but the proportion of planning the last quit attempt was slightly higher

among NRT users than non-NRT users. The intention to quit in next 30 days was higher among

NRT users than non-NRT users, and no intention to quit was higher among non-NRT users than

NRT users. NRT users were more likely to set a quit date for the planned quit attempt than non-

NRT users. NRT users were more likely to perceive themselves to be very addicted to cigarette

smoking, be less confident to quit smoking, and perceive that it would be hard for them to quit

smoking than non-NRT users. However, NRT users had higher motivation to quit smoking, as

they perceived that quitting smoking would benefit them a lot, and they would quit for reducing

disease risk and improving health more than non-NRT users. The proportion of home smoking

restrictions (no indoor smoking) was much higher among non-NRT users (58%) than NRT users

(48% for NRT use <8 weeks and 38% for NRT use ≥8 weeks). NRT users reported a higher

proportion of seeing or hearing an advertisement about stop smoking medications such as

56

nicotine patches and gum than non-NRT users (66%), especially among those who used NRT ≥8

weeks (79%). There were no differences in social support for quitting (be able to count on

someone to support quitting or some would make it difficult to quit smoking) or other members

smoking in the household between NRT and non-NRT users. NRT users were more likely to use

other quit aids, including other pharmaceutical aids (bupropion SR and varenicline), behavioral

support, and other methods (e.g., hypnosis, laser therapy, and self-help materials) at baseline

than non-NRT users. More NRT users perceived that quit medication would make quitting easier

(78% for NRT use <8 weeks and 85% for NRT use ≥8 weeks) than non-NRT users (68%). Those

who used NRT <8 weeks (63%) were more likely to perceive that the cost of quit medications

made it difficult to use than non-NRT users (56%) and those who used NRT ≥8 weeks (56%).

There were no differences in concern about the side effects of quit medications and difficulty of

obtaining quit medications (Table 8).

At follow-up, NRT users made more serious quit attempts than non-NRT users. However, non-

NRT users had a higher proportion of quitting for at least one month at the end of the 18 month

follow-up or during any follow-up period, and had quit for more days than NRT users. NRT

users were more likely to use other pharmaceutical quit aids and behavioral support at follow-up

than non-NRT users. Non-NRT users were more likely to be able to count on someone to support

quitting and have home smoking restrictions, but less likely to have someone make quitting

difficult or to see or hear an ad about stop smoking medications, than NRT users. There was no

difference in time in the study between NRT and non-NRT users (Table 8).

B. Comparison between NRT users with use duration <8 weeks and ≥8 weeks

The two NRT use groups were very similar, especially on smoking related variables, including

nicotine dependence, quit history, beliefs about quitting, motivation for quitting, and quit aid use.

The major differences at baseline were age (those who used NRT <8 weeks were younger),

indoor smoke-free restrictions (higher among those who used NRT <8 weeks), and seeing or

hearing an ad about stop smoking medications (lower among those who used NRT <8 weeks). At

follow-up, there were no differences in number of serious quit attempts, use of other

57

pharmaceutical aids, behavioural support, other quit methods, and beliefs about quit medications

between the two NRT use groups. Those who used NRT <8 weeks (15%) had a higher

proportion of using other tobacco products than those who used NRT ≥8 weeks (7%). Those who

used NRT <8 weeks were more likely to be able to count on someone to support quitting, and

more likely to have other household members smoking than those who use NRT ≥8 weeks. With

regard to quitting outcomes, those who used NRT ≥8 weeks had higher proportions on all

quitting outcomes (quit ≥1 month at the end of 18 months of follow-up and at any follow-up, quit

≥12 months at the end of 18 months of follow-up and at any follow-up, and longest quit days

during 18 month follow-up) than those who used NRT <8 weeks (Table 8).

58

Table 8. Characteristics of respondents who made serious quit attempts at follow-up: by NRT use duration, OTS longitudinal study 2005-2009

Non‐use (N=933 )

Use <8 wks (N=535 )

Use ≥8 wks (N=122 )

Timing Characteristics % % %

Baseline Socio‐demographic characteristics Age (years) Mean (SD)† 41.2 (15.0)a 42.9 (13.4) b 49.6 (13.4) Median (min‐max) 40.0 (18‐88) 44.0 (18‐78) 50.0 (18‐82) 18‐24 16.2 a 12.1 b 3.3 25‐39 31.8 26.6 14.9 40‐54 31.7 43.3 45.5 55‐64 12.9 12.8 27.3 65+ 7.5 5.3 9.1 Sex Female 54.2 a 60.8 62.3 Education <High school 15.4 16.7 14.9 High school 30.3 31.0 25.6 Some post‐secondary 11.7 11.2 13.2 Post‐secondary graduation 42.5 41.1 46.3 Marital status Never married 26.6 a 18.6 18.9 Married/common law 52.2 56.5 51.6 Widowed/separated/divorced 21.2 24.9 29.5 General health Self‐perceived health Good – Excellent 80.1 a 72.9 77.1 Poor – Fair 19.9 27.1 22.9 Nicotine dependence Smoking status Daily 70.1 a 85.6 87.7 Occasionally 29.9 14.4 12.3 Cigarettes per day Mean (SD)† 12.7 (9.7) a 16.3 (9.3) 17.1 (12.5) Median (min‐max) 10.6 (1‐90) 15.0 (1‐75) 15.0 (1‐82) 1‐10 cigarettes/day 45.8 a 30.1 32.0 11‐20 cigarettes/day 38.6 41.1 28.5 21+ cigarettes/day 15.7 28.8 29.5 Heaviness of smoking index Low 37.3 a 22.9 24.1 Moderate 39.8 41.0 38.0 High 22.9 36.0 38.0 Using other tobacco (e.g., cigar,

snus) 10.4 8.8 6.7

59

Past quit history # of lifetime quit attempts Mean (SD)† 3.6 (8.7) a 4.4 (7.3) 5.1 (9.7) Median (min‐max) 2.0 (0‐200) 3.0 (0‐100) 3.0 (0‐100) Tried to quit in the last 12 months 70.0 a 60.6 63.9 Planned the most recent quit

attempt 17.3 a 22.8 22.1 Intention to quit Intention to quit Within the next 30 days 20.3 a 25.8 34.4 Within 1‐6 months 31.9 35.9 33.6 Beyond next 6 months 27.4 24.5 18.0 No intention to quit 12.7 8.4 8.2 Not applicable 7.7 5.5 5.8 A firm date for the planned quit

attempt 11.8 14.4 17.2 Beliefs about addiction and

quitting Self‐perceived addiction Not at all to somewhat addicted 47.2 a 21.3 20.5 Very addicted 52.8 78.7 79.5 Self‐perceived easiness to quit Somewhat to very easy 25.4 a 7.7 9.0 Somewhat to very hard 74.6 92.3 91.0 Self‐perceived confidence to quit

completely Fairly to very confident 67.2 a 56.1 59.0 Not very to not at all confident 32.8 43.9 41.0 Motivational variables for quitting Perceived benefit from quitting Quite a lot to a lot 77.7 a 87.5 89.3 Not at all to little 22.3 12.5 10.7 Main reason for planning to quit To reduce disease risk or improve

health 33.4 a 42.2 45.9 Social‐environmental factors for


support quitting

81.0

82.8

79.8 Someone making quitting difficult 46.5 46.9 47.5 Other household member(s)

smoking 5.3 6.0 4.9 No indoor smoking at home 58.0 a 48.4 b 37.7 Workplace smoking ban 74.5 72.8 66.7 Seeing or hearing an ad about stop

smoking medications such as nicotine patch and gum 66.4 69.0 b 78.7

60

Quit aids Ever use of quit aid patterns Ever used NRT‡ to quit smoking 41.3 a 80.9 87.7 Ever used other pharmaceutical

aids§ 21.5 a 40.8 38.5 Ever used behaviour support¶ 12.3 a 19.8 14.8 Ever used other quit methods†† 23.3 a 42.6 50.8 Ever use of NRT‡ in combina on

with others None 42.8 a 10.5 9.8 NRT‡ only 17.9 23.9 22.1 NRT‡ and other pharmaceu cal

aids§ 6.7 14.6 13.1 NRT‡ and behavioural support¶ 1.7 3.4 2.5 NRT‡ and other quit methods†† 4.5 13.6 23.0 NRT‡ and two or more other quit

aids‡‡ 10.5 25.4 27.1 All other quit aids‡‡ without NRT 16.0 8.6 2.5 Beliefs about quit medications Using medications making

quitting easier 67.6 a 77.6 85.3 Difficult to use medications due

to the cost 56.1 a 63.2 55.7 Hard to get quit medications 9.2 10.3 7.4 Concerning the side effects 39.8 38.3 36.1

Follow‐up


Mean (SD) 2.5 (2.8) a 3.3 (3.8) 3.7 (4.4) Median (min‐max) 2.0 (1‐37) 2.0 (1‐40) 2.5 (1‐41) Quit ≥ 1 month at follow‐up 3 29.0 a 19.6 b 29.0 Quit ≥ 12 months at follow‐up 3 5.6 2.6 b 7.0 Quit ≥ 1 month at any follow‐up 52.6 a 36.5 b 67.2 Quit ≥ 12 months at any follow‐up 5.8 2.8 b 9.0 Continuous abstinence from

baseline to FU1 2.3 0.6 b 3.5 Continuous abstinence from

baseline to FU2 1.2 0.6 1.7 Continuous abstinence from

baseline to FU3 1.0 0.4 1.8 Longest quit days during any

follow‐up Mean (SD) 88.0 (124.6)a 55.4 (94.1) b 109.3 (133.7) Median (min‐max) 42.0 (0‐666) 14.0 (0‐579) 84.0 (0‐580) Other quit aids at follow‐up Other pharmaceutical aids§ 16.8 18.3 18.9 Behavioural support¶ 13.8 a 24.9 23.0 Other quit methods†† 16.7 a 32.2 29.5

61

Using other tobacco (e.g., cigar, snus) at FU 15.8 15.3 b 7.4

Social‐environmental factors for quitting

Able to count on someone to support quitting 82.7 a 89.4 b 77.1

Someone making quitting difficult 53.6 a 63.0 54.9 Other household member(s)

smoking 18.0 20.9 b 10.7 No indoor smoking at home 74.2 a 67.3 68.0 Seeing or hearing an ad about stop

smoking medications such as nicotine patch and gum 84.7 a 89.0 93.4

Follow‐up time Time in the study at follow‐up 1 Mean (SD)† days 185.8 (11.8) 185.7 (13.8) 184.3 (8.3) Median (min‐max) days 182.0 (167‐

285) 182.0 (166‐311) 182.0 (167‐228) Time in the study at follow‐up 2 Mean (SD)† days 373.1 (17.6) 372.0 (16.9) 369.6 (12.1) Median (min‐max) days 369.0 (346‐502) 367.0 (346‐502) 366.0 (352‐414) Time in the study at follow‐up 3 Mean (SD)† days 558.0 (20.7) 557.4 (22.2) 553.6 (17.3) Median (min‐max) days 553.0 (523‐697) 552.0 (519‐685) 550.0 (517‐626) a P value < 0.05 for the comparison between NRT and non‐NRT users. b P value < 0.05 for the comparison between using NRT <8 weeks and ≥8 weeks. † SD, standard devia on for un‐weighted sample; SE, standard error for weighted sample. ‡ NRT, including any use of nico ne patches, gum, inhaler and lozenges. § Other pharmaceutical aids including bupropion SR and varenicline . ¶ Behavioural support including group counselling, specialized addiction counselling, Ontario Quitline, smokers helpline online, and taking parting in a quit program. †† Other methods including hypnosis, acupuncture, laser therapy, self‐help booklet or video, a website or a chat group to help quit smoking. ‡‡ Other quit aids, including other pharmaceutical aids (e.g., bupropion or varenicline), behavioural support (e.g., counselling), and other methods (e.g., hypnosis and laser therapy).

62

6.1.6 Baseline and Follow-up Characteristics of Respondents: By Quitting Outcome

Baseline and follow-up characteristics of respondents by quit patterns based on their quitting

outcome during any follow-up among those who made a serious quit attempt are presented

below. Three quit groups were identified: those who did not quit (no-quitters), those who quit ≥1

month but <12 months (short-term quitters), and those who quit ≥12 months (long-term quitters).

Those who quit less than one month were treated as “did not quit”. Overall, 52% of respondents

(i.e., current smokers at baseline) did not quit smoking at follow-up, 43% were short-term

quitters, and 5% were long-term quitters.

A. Comparison between non-quitters and quitters

Quitters and non-quitters were very similar with regard to socio-demographic characteristics,

except for education. The proportion of respondents with post-secondary graduation was higher

among quitters (45%) than non-quitters (39%). There was no difference in self-perceived health

between quitters and non-quitters. Non-quitters were more likely to be daily and heavy smokers

(>20 cigarettes/day) with a high level of HSI and to smoke more cigarettes per day than quitters.

There were no differences between quitters and non-quitters in using other tobacco at baseline,

trying to quit in the 12 months prior to baseline, number of lifetime quit attempts, and planning

the last quit attempt. Non-quitters were more likely than quitters to perceive themselves to be

very addicted to cigarette smoking, to be less confident to quit smoking, and to perceive that it

would be difficult for them to quit smoking. However, there were no differences in intention to

quit and setting a quit date for the planning quit attempt between these two groups. More non-

quitters perceived that they would benefit a lot from quitting than quitters, but both groups had a

similar main reason for planning to quit (i.e., reducing disease risk or improving health). Non-

quitters were more likely to ever use NRT and behaviour support at baseline than quitters, but

there was no difference in beliefs about quit medications. At follow-up, there were no differences

in number of serious quit attempts, use of NRT, other quit aids and other tobacco products, and

seeing or hearing an ad about stop smoking medications between these two groups, nor the time

in the study. However, non-quitters were more likely to be able to count on someone to support

quitting, more likely to have someone make quitting more difficult, and more likely to have other

63

household members smoking, but less likely to have home smoking restrictions than quitters

(Table 9).

B. Comparison between short-term and long-term quitters

Short-term and long-term quitters were very similar in socio-demographic characteristics,

general health, motivation to quit, most variables in relation to nicotine dependence, beliefs

about quitting, using other tobacco products at baseline and follow-up, quit aid use at baseline

and follow-up, beliefs about quit medications at baseline, and time in the study. The major

differences included daily smoking (higher rate in short-term quitters), number of lifetime quit

attempts (more quit attempts in short-term quitters), trying to quit in the last 12 months prior to

baseline (higher in short-term quitters), intention to quit (no intention to quit: higher in short-

term quitters), social support for quitting at baseline and follow-up (someone making quitting

difficult: higher in short-term quitters), home smoking restrictions at baseline and follow-up (no

indoor smoking: lower in short-term quitters), and other household members smoking at follow-

up (higher in short-term quitters) (Table 9).

64

Table 9. Characteristics of respondents who made serious quit attempts at follow-up: by quitting outcome, OTS longitudinal study 2005-2009

Non‐quitter (N=822 )

Quit≥1‐<12m (N=688 )

Quit≥12m (N=80 )

Timing Characteristics % % %


Age (years) Mean (SD)† 42.3 (14.5) 42.5 (14.7) 42.6 (13.1) Median (min‐max) 43.0 (18‐88) 42.5 (18‐87) 42.0 (19‐74) 18‐24 15.0 13.0 7.6 25‐39 25.9 31.1 36.7 40‐54 38.6 34.8 31.7 55‐64 13.8 13.5 20.3 65+ 6.6 7.6 3.8 Sex Female 57.5 57.3 50.0 Education <High school 17.8 a 13.5 15.0 High school 30.0 30.6 28.8 Some post‐secondary 12.8 10.4 11.3 Post‐secondary graduation 39.4 45.6 45.0 Marital status Never married 23.4 23.5 21.3 Married/common law 53.0 54.0 56.3 Widowed/separated/divorced 23.6 22.5 22.5 General health Self‐perceived health Good – Excellent 76.9 78.2 76.3 Poor – Fair 23.1 21.8 23.8 Nicotine dependence Smoking status Daily 86.3 a 67.6 b 56.3 Occasionally 13.7 32.4 43.8 Cigarettes per day Mean (SD)† 15.7 (10.2) a 12.8 (9.7) 12.6 (9.1) Median (min‐max) 15.0 (1‐90) 10.6 (1‐82) 11.0 (1‐50) 1‐10 cigarettes/day 34.6 a 44.9 42.5 11‐20 cigarettes/day 39.5 39.0 42.5 21+ cigarettes/day 25.9 16.1 15.0 Heaviness of smoking index Low 24.0 a 39.9 40.4 Moderate 43.4 35.7 36.5 High 32.6 24.3 23.1 Using other tobacco (e.g., cigar,

snus) 9.7 9.0 12.5

65

Past quit history # of lifetime quit attempts Mean (SD)† 4.0 (6.1) 4.1 (10.7) b 2.8 (3.8) Median (min‐max) 3.0 (0‐66) 2.0 (0‐200) 2.0 (0‐25) Tried to quit in the last 12

months 35.9 32.4 b 21.3 Planned the most recent quit

attempt 19.5 19.9 16.3 Intention to quit Intention to quit Within the next 30 days 22.0 24.7 b 22.5 Within 1‐6 months 33.6 33.7 28.8 Beyond next 6 months 28.8 22.0 26.3 No intention to quit 10.8 11.9 2.5 Not applicable 4.7 7.7 20.0 A firm date for the planned quit


quitting Self‐perceived addiction Not at all to somewhat

addicted 26.6 a 46.7 48.8 Very addicted 73.4 53.3 51.3 Self‐perceived easiness to quit Somewhat to very easy 11.1 a 25.7 26.2 Somewhat to very hard 88.9 74.3 73.8 Self‐perceived confidence to quit

completely Fairly to very confident 58.3 a 68.9 b 57.5 Not very to not at all confident 41.7 31.0 42.5 Motivational variables for

quitting Perceived benefit from quitting Quite a lot to a lot 85.4 a 78.3 76.3 Not at all to little 14.6 21.7 23.7 Main reason for planning to quit To reduce disease risk or

improve health 37.5 37.7 33.8 Social‐environmental factors for


support quitting 81.5 82.7 b 70.0 Someone making quitting

difficult 48.4 46.8 b 28.8 Other household member(s)

smoking 6.5 4.4 5.0 No indoor smoking at home 47.2 a 59.0 b 65.0 Seeing or hearing an ad about 67.4 69.0 68.8

66

stop smoking medications such as nicotine patch and gum

Quit aids Ever use of quit aid patterns Ever used NRT‡ to quit

smoking 63.3 a 52.9 51.3 Ever used other

pharmaceutical aids§ 30.5 28.3 25.0 Ever used behaviour support¶ 16.9 a 12.8 15.0 Ever used other quit

methods†† 33.2 30.5 30.0 Ever use of NRT‡ in combina on

with others None 24.8 a 34.2 35.0 NRT‡ only 21.1 19.5 18.8 NRT‡ and other

pharmaceutical aids§ 11.0 8.6 8.8 NRT‡ and behavioural

support¶ 3.4 0.9 3.8 NRT‡ and other quit

methods†† 10.2 7.9 6.3 NRT‡ and two or more other

quit aids‡‡ 17.6 16.1 13.8 All other quit aids‡‡ without

NRT 11.9 12.9 13.8 Beliefs about quit medications Using medications making

quitting easier 71.4 72.7 78.8 Difficult to use medications

due to the cost 59.1 58.9 47.5 Hard to get quit medications 9.6 9.3 8.8 Concerning the side effects 40.2 38.4 32.5

Follow‐up


Mean (SD) 1.5 (3.1) 1.5 (2.4) 1.2 (1.8) Median (min‐max) 1.0 (0‐41) 1.0 (0‐22) 1.0 (0‐10) Quit aids at follow‐up NRT use Not using NRT 57.8 65.6 67.5 Using NRT <8 weeks 38.7 25.7 18.8 Using NRT ≥8 weeks 3.5 8.7 13.7 Other pharmaceutical aids§ 15.8 19.8 15.0 Behavioural support¶ 18.7 17.7 17.5 Other quit methods†† 24.8 21.1 18.8 Using other tobacco

(e.g., cigar, snus) at FU 15.5 15.0 10.0

67

Social‐environmental factors for quitting

Able to count on someone to support quitting 92.5 a 82.6 b 17.5

Someone making quitting difficult 64.4 a 54.1 b 3.8

Other household member(s) smoking 22.8 a 15.1 b 2.5

No indoor smoking at home 61.2 a 80.8 b 95.0 Seeing or hearing an ad about

stop smoking medications such as nicotine patch and gum 87.2 85.9 90.0

Follow‐up time Time in the study at follow‐up 1 Mean (SD)† days 185.8 (11.8) 185.7 (13.8) 184.3 (8.3) Median (min‐max) days 182.0 (167‐ 285) 182.0 (166‐311) 182.0 (167‐228) Time in the study at follow‐up 2 Mean (SD)† days 373.1 (17.6) 372.0 (16.9) 369.6 (12.1) Median (min‐max) days 369.0 (346‐502) 367.0 (346‐502) 366.0 (352‐414) Time in the study at follow‐up 3 Mean (SD)† days 558.0 (20.7) 557.4 (22.2) 553.6 (17.3) Median (min‐max) days 553.0 (523‐697) 552.0 (519‐685) 550.0 (517‐626) a P value < 0.05 for the comparison between NRT and non‐NRT users. b P value < 0.05 for the comparison between using NRT <8 weeks and ≥8 weeks. † SD, standard deviation for un‐weighted sample; SE, standard error for weighted sample. ‡ NRT, including any use of nicotine patches, gum, inhaler and lozenges. § Other pharmaceutical aids including bupropion SR and varenicline . ¶ Behavioural support including group counselling, specialized addiction counselling, Ontario Quitline,

smokers helpline online, and taking parting in a quit program. †† Other methods including hypnosis, acupuncture, laser therapy, self‐help booklet or video, a website

or a chat group to help quit smoking. ‡‡ Other quit aids, including other pharmaceutical aids (e.g., bupropion SR and varenicline), behavioural


68

6.2 Descriptive Analysis of the Sensitivity Analysis

Smokers use NRTs in two ways to help reduce harm from smoking, by quitting and by reducing

smoking. In general population studies, the effect of NRT use is usually examined among those

who make a serious quit attempt. This approach may have misclassified those who tried to quit

and used NRTs, but failed to quit, and thus changed their intention from quitting to reducing.

A sensitivity analysis is conducted to examine if the magnitude of NRT effect would be different

for the respondents who made a serious quit attempt or reduced smoking from those who made a

serious quit attempt. This sensitivity analysis may be able to assess the effectiveness of NRT use

in the general population overall, using NRT either for quitting or for reducing smoking

(assuming reducing smoking would lead to cessation at some stage). Among the 4,064 current

smokers at baseline, 2,695 respondents either made a serious quit attempt or reduced smoking at

follow-ups one, two, and three.

6.2.1 Comparison of Respondents between the Two Analyses

Respondents in the main and sensitivity analyses were very similar in social demographic

characteristics and general health (difference in percentage <3%, and in mean and median <1).

Daily smoking and cigarettes per day smoked among participants between the two studies were

very similar, too, but there were a lower proportion of low level of HSI and a higher proportion

of high level of HSI in the sensitivity analysis than the main analysis. The number of lifetime

quit attempts and the proportion of planning the most quit attempt were similar in the two

analyses, but smokers in the sensitivity analysis had a lower proportion of quit attempts in the

last 12 months prior to the baseline survey than in the main analysis. Smokers in the sensitivity

analysis had a lower proportion of intention to quit in the next 30 days, but a higher proportion of

intention to quit beyond next six months or no intention to quit than those in the main analysis.

Smokers in both studies had similar beliefs about their addiction, confidence of quitting, self-

perceived easiness of quitting, and perceived benefit from quitting. Smokers in the main analysis

had a higher proportion of planning to quit for the reason to reduce disease risk or improve

health than those in the sensitivity analysis. The social-environmental factors for quitting (e.g.,

69

other household members smoking and home smoking restrictions) were similar in the two

analyses. Smokers in the sensitivity analysis were less likely to use NRT than those in the main

analysis, although smokers in both analyses expressed similar beliefs about the effects of quit

medications. Smokers had lower quit rates on short-term quit and fewer quit days in the

sensitivity analysis than the main analysis. At follow-up, smokers were less likely to use NRT

and have home smoking restrictions in the sensitivity analysis than in the main analysis. (Table

10).

In summary, smokers in the sensitivity analysis were more likely to be highly dependent on

tobacco smoking, less likely to make quit attempts in the near future, less likely to use NRT, and

had lower rates of short-term quit. (For information on questions used to identify participants and

flow chart of participants, please see Appendix 10: Sensitivity Analysis).

70

Table 10. Comparison of respondents in the main and sensitivity analyses, OTS longitudinal study 2005-2009

Main analysis (N = 1,590)

Sensitivity analysis (N = 2,695) Absolute

difference Timing Characteristics n % n %


Age (years) Mean (SD or SE)† 42.4 14.5 43.7 14.5 0.4 Median (min‐max) 43 18‐88 44 18‐88 1.0 18‐24 218 13.8 326 12.1 1.7% 25‐39 454 28.7 702 26.1 2.6% 40‐54 579 36.6 1020 37.9 1.3% 55‐64 221 14.0 412 15.3 1.3% 65+ 109 6.9 220 8.2 1.3% Sex Female 907 57.0 1533 56.9 0.1% Education <High school 248 15.8 449 16.7 0.9% High school 473 30.2 803 29.8 0.2% Some post‐secondary 183 11.7 324 12.0 0.3% Post‐secondary graduation 663 42.3 1080 40.1 2.2% Marital status Never married 370 23.4 593 22.0 1.4% Married/common law 849 53.6 1447 53.7 0.1% Widowed/separated/divorced 365 23.0 644 23.9 0.9% General health Self‐perceived health Good – Excellent 1231 77.4 2135 79.2 1.8% Poor – Fair 359 22.6 560 20.8 1.8% Nicotine dependence Smoking status Daily 1219 76.7 2182 81.0 4.3% Occasionally 371 23.3 513 19.0 4.3% Cigarettes per day Mean (SD) † 14.3 10.0 14.7 9.6 0.4 Median (min‐max) 12 1‐90 12.3 1‐90 0.3 1‐10 cigarettes/day 627 39.4 963 35.7 3.7% 11‐20 cigarettes/day 627 39.4 1131 42.0 0.6% 21+ cigarettes/day 336 21.1 601 22.3 1.2% Heaviness of smoking index Low 543 34.2 786 29.2 5.0% Moderate 595 37.4 1052 39.0 1.8% High 179 11.3 472 17.5 6.2% Unknown 273 17.2 385 14.3 2.9% Using other tobacco

(e.g., cigar, snus) 152 9.6 249 9.2 0.4%

71

Past quit history # of lifetime quit attempts Mean (SD)† 4.0 8.3 3.4 6.8 0.6 Median (min‐max) 2 0‐200 2 0‐200 0.0 Tried to quit in the last 12

months 535 33.7 703 26.1 7.6% Planned the most recent quit

attempt 310 19.5 487 18.1 1.4% Beliefs about quitting Intention to quit Within the next 30 days 369 23.2 437 16.2 7.0% Within 1‐6 months 531 33.4 786 29.2 4.2% Beyond next 6 months 409 25.7 885 32.8 7.1% No intention to quit 173 10.9 438 16.3 5.4% Not applicable 108 6.8 149 5.5 1.3% A firm date for the planned quit

attempt 208 13.1 261 9.7 3.4% Self‐perceived addiction Not at all to somewhat

addicted 579 36.4 997 37.0 0.6% Very addicted 1011 63.6 1698 63.0 0.6% Self‐perceived easiness to quit Somewhat to very easy 289 18.2 533 19.8 1.6% Somewhat to very hard 1301 81.8 2162 80.2 1.6% Self‐perceived confidence to

quit completely Fairly to very confident 999 62.8 1628 60.4 1.4% Not very to not at all

confident 591 37.2 1067 39.6 1.4% Motivational variables for

quitting Perceived benefit from quitting Quite a lot to a lot 1302 81.9 2113 78.4 3.5% Not at all to little 288 18.1 582 21.6 3.5% Main reason for planning to quit To reduce disease risk or

improve health 594 37.4 772 28.7 8.7% Social‐environmental factors

for quitting Able to count on someone to

support quitting 1295 81.5 2202 81.7 0.2% Someone making quitting

difficult 743 46.7 1197 44.4 2.3% Other household member(s)

smoking 87 5.5 159 5.9 0.4% No indoor smoking at home 846 53.2 1305 48.4 4.8% Seeing or hearing an ad about

stop smoking medications such 1084 68.2 1793 66.5 1.7%

72

as nicotine patch and gum Quit aids Ever use of quit aid patterns Ever used NRT‡ to quit

smoking 925 58.2 1442 53.5 4.7% Ever used other

pharmaceutical aids§ 466 29.3 675 25.1 4.2% Ever used behaviour support¶ 239 15.0 353 13.1 1.9% Ever used other methods†† 507 31.9 765 28.4 3.5% Ever use of NRT‡ in combina on

with others None 467 29.4 927 34.4 5.0% NRT‡ only 322 20.3 558 20.7 0.4% NRT‡ and other

pharmaceutical aids§ 156 9.8 218 8.1 1.7% NRT‡ and behavioural

support¶ 37 2.3 56 2.1 0.2% NRT‡ and other quit

methods†† 143 9.0 232 8.6 0.4% NRT‡ and two or more other

quit aids 267 16.8 378 14.0 2.8% All other quit aids††† without

NRT 198 12.5 326 12.1 0.4% Beliefs about quit medications Using medications making

quitting easier 1150 72.3 1886 70.0 2.3% Difficult to use medications

due to the cost 652 41.0 1108 41.1 0.1% Hard to get quit medications 150 9.4 271 10.1 0.7% Concerning the side effects 620 39.0 1094 40.6 1.6%

Follow ‐up


Mean (SD) 2.9 3.3 1.6 2.2 1.7 Median (min‐max) 2 1‐41 1 1‐41 1.0 Quit ≥ 1 month at follow‐up 3 353 25.8 373 16.4 9.4% Quit ≥ 12 months at follow‐up 3 64 4.7 65 2.9 1.8% Quit ≥ 1 month at any follow‐up 768 48.3 982 36.4 11.9% Quit ≥ 12 months at any follow‐

up 80 5.0 82 3.0 2.0% Continuous abstinence from

baseline to FU1 27 1.8 28 1.1 0.7% Continuous abstinence from

baseline to FU2 15 1.0 15 0.6 0.4% Continuous abstinence from

baseline to FU3 12 0.9 12 0.5 0.4% Longest quit days during any

follow‐up

73

Mean (SD) 78.7 117.3 56.2 98.9 22.5 Median (min‐max) 28 0‐666 14 0‐666 14.0 Quit aids NRT‡ use dura on at

follow‐up 1 Mean (SD) days among users 22.2 33.9 21.7 33.6 0.5 Median (min‐max) days

among users 9 1‐183 7 1‐183 2.0 Not using NRT 1131 75.1 2115 82.6 7.5% Using NRT‡ <8 weeks 332 22.0 395 15.4 6.6% Using NRT‡ ≥8 weeks 44 2.9 51 2.0 0.9% All quit aid use patterns at

follow‐up 1 None 898 59.6 1800 70.3 10.7% NRT‡ only 241 16.0 295 11.5 4.5% NRT‡ and other




quit aids‡‡ 42 2.8 46 1.8 1.0% All other quit aids‡‡ without

NRT 224 14.9 306 12.0 2.9% NRT‡ use dura on at

follow‐up 2 Mean (SD) days among users 29.2 44.1 27.6 43.0 1.6 Median (min‐max) days







NRT 207 14.2 289 11.9 2.3%

74

NRT‡ use dura on at follow‐up 3

Mean (SD) days among users 28.5 46.2 28.1 47.7 0.4 Median (min‐max) days







NRT 192 14.0 270 11.9 2.1% Times of NRT use during all

three follow‐ups None 933 58.7 1868 69.3 10.6% At least at one follow‐up 378 23.8 519 19.3 4.5% At least at two follow‐ups 198 12.5 222 8.2 4.3% At all three follow‐ups 81 5.1 86 3.2 1.9% NRT use duration during 18

month follow‐up Mean (SD) days among users 40.9 71.1 37.8 68.8 3.1 Median (mix‐max) days

among users 15.0 1‐720 14.0 1‐720 1.0 Using other tobacco at any

follow‐up 238.0 15.0 379 14.1 0.9% Social‐environmental factors

for quitting Able to count on someone to

support quitting 1344 84.5 2360 87.6 3.1% Someone making quitting

difficult 904 56.9 1517 56.3 0.6% Other household member(s)

smoking 293 18.4 545 20.2 1.8% No indoor smoking at home 1135 71.4 1742 64.6 6.8% Seeing or hearing an ad about

stop smoking medications such as nicotine patch and gum 1380 86.8 2305 85.5 1.3%

75

Follow‐up time Time in the study at follow‐up 1 Mean (SD)† days 185.6 12.3 185.2 11.4 0.4 Median (min‐max) days 182.0 166‐311 182.0 158‐311 0.0 Time in the study at follow‐up 2 Mean (SD)† days 372.4 17.0 371.7 16.3 0.7 Median (min‐max) days 368.0 346‐502 367.0 337‐502 1.0 Time in the study at follow‐up 3 Mean (SD)† days 557.4 21.0 556.2 20.4 1.2 Median (min‐max) days 553.0 517‐697 552.0 507‐697 1.0

† SD, standard deviation for un‐weighted sample; SE, standard error for weighted sample. ‡ NRT, including any use of nicotine patches, gum, inhaler and lozenges. § Other pharmaceutical aids including bupropion SR and varenicline. ¶ Behavioural support including group counselling, specialized addiction counselling, Ontario Quitline,

smokers helpline online, and taking parting in a quit program. †† Other methods including hypnosis, acupuncture, laser therapy, self‐help booklet or video, and a

website or a chat group to help quit smoking. ‡‡ Other quit aids, including other pharmaceu cal aids (e.g., bupropion SR and varenicline ), behavioural


76

Chapter 7: Analyses of Associations of NRT Use Duration and Smoking Cessation

Four categorical outcomes were included in the main analysis: 1) short-term abstinence

(continuous abstinence ≥1 month) at the end of 18 months of follow-up; 2) long-term abstinence

(continuous abstinence ≥12 months) at the end of 18 months of follow-up; 3) short-term

abstinence at any period of follow-up; and 4) long-term abstinence at any period of follow-up.

7.1 Short-Term Abstinence (Continuous Quitting ≥1 Month) at the End of 18 Months of Follow-up Based on QIC values, it was found that non-linearity existed for short-term abstinence at the end

of 18 months of follow-up by all three quit aid use durations. No overdispersion was found in the

Poisson models for the associations between quit aid use duration (for any NRT, patches, and

gum) and short-term abstinence at the end of 18 months of follow-up. Poisson models with

robust standard errors were applied.

7.1.1 by any NRT use duration

The Poisson model was best fitted with four categories of any NRT use duration (i.e., non-use

and use <4, ≥4-<8, and ≥8 weeks, based on the longest use duration at any one follow-up). The

proportion of short-term abstinence at the end of 18 months of follow-up was 29.0%, 17.2%,

29.4%, and 29% for not using any NRT, using any NRT <4 weeks, using any NRT between ≥4

and <8 weeks, and using any NRT ≥8 weeks, respectively. For any NRT use duration with four

categories, the crude analysis showed that those who used any NRT <4 weeks were 41% less

likely to quit ≥1 month at the end of 18 months of follow-up than those who did not use any

NRT. Using any NRT ≥4 weeks was not associated with short-term abstinence at the end of 18

months of follow-up, compared to not using any NRT. For any NRT use duration with three

categories, using any NRT <8 weeks was associated with a 32% lower likelihood of short-term

abstinence than not using any NRT. Using any NRT ≥8 weeks was associated with a 1.5 times

higher likelihood of short-term abstinence than using any NRT <8 weeks. There was no

difference between using any NRT ≥8 weeks and not using any NRT in short-term abstinence

(Table 11).

77

Table 11. Crude Poisson regression analysis: association between any NRT use duration and short-term abstinence (continuous quitting ≥1 month) at the end of 18 months of follow-up among baseline smokers who made serious quit attempts at follow-up and were re-interviewed 18 months later (n=1,368), OTS longitudinal study 2005-2009

Quit aid

Sample size

n (%)

% of quitting Relative Risk

(RR)

95% Confidence Interval

(CI) P value Model ≥1 month Three groups for NRT use duration, based on the longest use at any one follow-up Non-use 1 790 (57.8) 29.0% Referent -------- <8 weeks 464 (33.9) 19.6% 0.68 0.55-0.84 0.0003 ≥8 weeks 114 (8.3) 29.0% 1.00 0.73-1.36 0.99 <8 weeks 2† 464 (33.9) 19.6% Referent -------- ≥8 weeks 114 (8.3) 29.0% 1.48 1.05-2.08 0.026 Four groups for NRT use duration, based on the longest use at any one follow-up (best fit model) Non-use 3 790 (57.8) 29.0% Referent <4 weeks 372 (27.2) 17.2% 0.59 0.46-0.76 <0.0001 ≥4 - <8 weeks 92 (6.7) 29.4% 1.01 0.72-1.42 0.94 ≥8 weeks 114 (8.3) 29.0% 1.00 0.73-1.36 0.99 † The model analysis included all three groups for NRT use duration; only the results for using NRT <8 weeks and ≥8 weeks are presented here.

For NRT use duration with three groups, the overall adjusted analysis showed that using any

NRT ≥8 weeks was associated with a 1.6 times higher likelihood of short-term abstinence than

using any NRT <8 weeks at the end of 18 months of follow-up. There was no difference in short-

term abstinence between using any NRT <8 weeks and not using any NRT, and between using

any NRT ≥8 weeks and not using any NRT (Table 12). Confounding factors adjusted for in this

model included baseline variables of daily smoking, cigarettes per day smoked, making a quit

plan for the last quit attempt, quit intention, self-perceived addiction, self-perceived easiness of

quitting, self-perceived benefit from quitting, and home smoking restrictions, and follow-up

variables of number of quit attempts and time in the study. Daily smoking was associated with a

lower likelihood of short-term abstinence than non-daily smoking. Other confounders were not

associated with short-term abstinence.

For NRT use duration with four groups, the overall adjusted analysis showed that using any NRT

<4 weeks was associated with a 26% lower likelihood of short-term abstinence and using any

NRT ≥4 weeks was not associated with short-term abstinence, compared to not using any NRT,

at the end of 18 months of follow-up (Table 12). Confounding variables adjusted for in this

78

model were the same as those for the model with three groups for any NRT use duration.

Similarly, daily smoking was associated with a lower likelihood of short-term abstinence than

non-daily smoking and other confounders were not associated with short-term abstinence. No

significant modifying variables were found for the association between any NRT use duration

(either with three groups or four groups) and short-term abstinence at the end of 18 months of

follow-up.

Table 12 . Adjusted Poisson regression analysis: association between any NRT use duration and short-term abstinence (continuous quitting ≥1 month) at the end of 18 months of follow-up among baseline smokers who made serious quit attempts at follow-up and were re-interviewed 18 months later (n=1,368), OTS longitudinal study 2005-2009

† Adjusted for baseline variables of daily smoking, cigarettes per day smoked, HSI, making a quit plan for the last quit attempt, quit intention, self‐perceived addiction, self‐perceived easiness of quitting, self‐perceived benefit from quitting, and home smoking restrictions, and follow‐up variables of number of quit attempts and time in the study for both models with three and four categories for NRT use duration.

‡ The model analysis included all three groups for NRT use duration; only the results for using NRT <8 weeks and ≥8 weeks are presented here.

Model Quit aid Relative risk (RR)† 95% Confidence Interval (CI)

P value

Three groups for NRT use duration, based on the longest use duration at any one follow-up 1 Non-use Referent -------- <8 weeks 0.85 0.68-1.07 0.16 ≥8 weeks 1.31 0.96-1.79 0.087 2 <8 weeks Referent‡ -------- ≥8 weeks 1.54 1.10-2.15 0.011 Four groups for NRT use duration, based on the longest use duration at any one follow-up (best fit model) 3 Non-use Referent -------- <4 weeks 0.74 0.57-0.96 0.023 ≥4 - <8 weeks 1.28 0.91-1.80 0.16 ≥8 weeks 1.32 0.96-1.81 0.091

79

7.1.2 by patch use duration

The Poisson model was best fitted by patch use duration with three groups (i.e., non-use, use <8

weeks, and use ≥8 weeks, based on the longest use duration at any one follow-up). The

proportion of short-term abstinence at the end of 18 months of follow-up was 27%, 19% and

34% for not using patches, using patches <8 weeks, and using patches ≥8 weeks, respectively.

The crude analysis showed that those who used patches ≥8 weeks were 1.8 times more likely to

quit ≥1 month at the end of 18 months of follow-up than those who used patches <8 weeks.

Those who used patches <8 weeks were 29% less likely to quit ≥1 month than those who did not

use patches. There was no difference in short-term abstinence between using patches ≥8 weeks

and not using patches (Table 13).

Table 13. Crude Poisson regression analysis: association between nicotine patch use duration and short-term abstinence (continuous quitting ≥1 month) at the end of 18 months of follow-up among baseline smokers who made serious quit attempts at follow-up and were re-interviewed 18 months later (n=1,368), OTS longitudinal study 2005-2009

Quit aid

Sample size

n (%)


(RR)


(CI) P value Model ≥1 month Three groups for patch use duration, based on the longest use duration at any one follow-up (best fit model)Non-use 1 1023 (74.8) 27.1% Referent -------- <8 weeks 281 (20.5) 19.2% 0.71 0.55-0.92 0.0097 ≥8 weeks 64 (4.7) 34.4% 1.27 0.89-1.81 0.19 <8 weeks 2 281 (20.5) 19.2% Referent† -------- ≥8 weeks 64 (4.7) 34.4% 1.79 1.18-2.71 0.0060 † The model analysis included all three groups for patch use duration; only the results for using patches <8 weeks and ≥8 weeks are presented here.

80

The overall adjusted analysis showed that using patches ≥8 weeks was associated with a 1.7

times higher likelihood of short-term abstinence than not using patches, and a 1.9 times higher

likelihood of short-term abstinence than using patches <8 weeks at the end of 18 months of

follow-up, and there was no difference between using patches <8 weeks and not using patches

(Table 14). Confounding variables adjusted for in this model included baseline variables of daily

smoking, cigarettes per day smoked, HSI, intention to quit, self-perceived addiction, self-

perceived easiness of quitting, self-perceived benefit from quitting, home smoking restrictions,

ever use of NRT, and ever use of other quit methods, and follow-up variables of use of other quit

methods and use of NRT other than patches. Daily smoking was associated with a lower

likelihood of short-term abstinence than non-daily smoking. Other confounders were not

associated with short-term abstinence. No significant modifying variables were found.

Table 14. Adjusted Poisson regression analysis: association between nicotine patch use duration and short-term abstinence (continuous quitting ≥1 month) at the end of 18 months of follow-up among baseline smokers who made serious quit attempts at follow-up and were re-interviewed 18 months later (n=1,368), OTS longitudinal study 2005-2009

† Adjusted for baseline variables of daily smoking, cigarettes per day smoked, HSI, quit intention, self‐perceived addiction, self‐perceived easiness of quitting, self‐perceived benefit from quitting, home smoking restrictions, ever use of NRT and ever use of other quit methods, and follow‐up variables of use of other quit methods and use NRT other than patches.

‡ The model analysis included all three groups for patch use duration; only the results for using patches <8 weeks and ≥8 weeks are presented here.

Model

Quit aid

Relative risk (RR)†

95% Confidence Interval (CI)

P value

Three groups for patch use duration, based on the longest use duration at any one follow-up (best fit model)1 Non-use Referent -------- <8 weeks 0.88 0.66-1.16 0.35 ≥8 weeks 1.74 1.21-2.50 0.0029 2 <8 weeks Referent‡ -------- ≥8 weeks 1.98 1.32-2.97 0.0009

81

7.1.3 by gum use duration

The Poisson model was best fitted by gum use duration with three groups (i.e., non-use, use <8

weeks, and use ≥8 weeks), based on the longest use duration at any one follow-up. The

proportion of short-term abstinence at the end of 18 months of follow-up was 27%, 19% and

32% for not using gum, using gum <8 weeks, and using gum ≥8 weeks, respectively. The crude

analysis showed that using gum <8 weeks was associated with a smaller likelihood of short-term

abstinence than not using gum. There was no difference in short-term abstinence between using

gum ≥8 weeks and not using gum or between using gum ≥8 weeks and using gum <8 weeks

(Table 15).

Table 15. Crude Poisson regression analysis: association between nicotine gum use duration and short-term abstinence (continuous quitting ≥1 month) at the end of 18 months of follow-up among baseline smokers who made serious quit attempts at follow-up and were re-interviewed 18 months later (n=1,368), OTS longitudinal study 2005-2009

Quit aid

Sample size

n (%)


(RR)


(CI) P value Model ≥1 month Three groups for gum use duration, based on the longest use duration at any one follow-up (best fit model)Non-use 1 1088 (79.5) 27.0% Referent -------- <8 weeks 239(17.5) 19.3% 0.71 0.54-0.94 0.017 ≥8 weeks 41 (3.0) 31.7% 1.17 0.74-1.86 0.50 <8 weeks 2 239 (17.5) 19.3% Referent† -------- ≥8 weeks 41 (3.0) 31.7% 1.65 0.98-2.77 0.059 † The model analysis included all three groups for gum use duration; only the results for using gum <8 weeks and ≥8 weeks are presented here.

82

The overall adjusted analysis showed that there were no differences in short-term abstinence at

the end of 18 months of follow-up between using gum ≥8 weeks and not using gum, between

using gum ≥8 weeks and using gum <8 weeks, and between using gum <8 weeks and not using

gum (Table 16). Confounding variables adjusted in this model included baseline variables of age,

education, daily smoking, cigarettes per day smoked, HSI, quitting attempt in the last 12 months,

quit intention, self-perceived addiction, self-perceived easiness of quitting, self-perceived benefit

from quitting, main reason to quit for reducing disease risk and improving health, home smoking

restrictions, and ever use of NRT, and ever use of bupropion SR or varenicline, and follow-up

variables of use of other quit methods and other NRT products without gum. Those with less

than high school education were less likely to quit than those with college/university graduation.

Daily smoking was associated with a lower likelihood of short-term abstinence than non-daily

smoking. Other confounders were not associated with short-term abstinence. No significant

modifying variables were found.

Table 16. Adjusted Poisson regression analysis: association between nicotine gum use duration and short-term abstinence (continuous quitting ≥1 month) at the end of 18 months of follow-up among baseline smokers who made serious quit attempts at follow-up and were re-interviewed 18 months later (n=1,368), OTS longitudinal study 2005-2009

† Adjusted for baseline variables of age, education, daily smoking, cigarettes per day smoked, HSI, making a quit attempt in last 12 months prior to baseline, quit intention, self‐perceived addiction, self‐perceived easiness of quitting, self‐perceived benefit from quitting, reducing disease risk and improving health as a main reason, home smoking restrictions, ever use of NRT, and ever use of bupropion SR or varenicline, and follow‐up variables of use of other quit methods and other NRT without gum.

‡ The model analysis included all three groups for gum use duration; only the results for using gum <8 weeks and ≥8 weeks are presented here.

Model Quit aid Relative risk (RR)† 95% Confidence Interval (CI) P value Three groups for gum use duration, based on the longest use duration at any one follow-up (best fit model) 1 Non-use Referent -------- <8 weeks 0.83 0.63-1.10 0.20 ≥8 weeks 1.19 0.76-1.86 0.45 2 <8 weeks Referent‡ -------- ≥8 weeks 1.43 0.87-2.37 0.16

83

7.2 Long-Term Abstinence (Continuous Quitting ≥12 Months) at the End of 18 Months of Follow-up The difference in QIC values showed that non-linearity existed for quit ≥12 months at the end of

18 months of follow-up by all three quit aid use durations, including any NRT, patches and gum.

There was no overdispersion in the Poisson models for the associations between quit aid use

duration for NRT, patches and gum (three categories) and quit ≥12 months at the end of 18

months of follow-up. Poisson models with robust standard errors were applied.

7.2.1 By any NRT use duration

The difference in QIC values showed that the Poisson model was best fitted by any NRT use

duration with three categories (i.e., non-use, use <8 weeks, and use ≥8 weeks), based on the

longest use duration at any one follow-up. The proportion of long-term abstinence at the end of

18 months of follow-up was 7%, 3%, and 8% for not using any NRT, using any NRT <8 weeks,

and using any NRT ≥8 weeks, respectively. The crude analysis showed that those who used any

NRT <8 weeks were 55% less likely to quit ≥12 months than those who did not use any NRT.

Using any NRT ≥8 weeks was associated with a 2.6 times higher likelihood of long-term

abstinence than using any NRT <8 weeks. There was no difference in long-term abstinence

between using NRT ≥8 weeks and not using NRT (Table 17).

Table 17. Crude Poisson regression analysis: association between any NRT use duration and long-term abstinence (continuous quitting ≥12 months) at the end of 18 months of follow-up among baseline smokers who made serious quit attempts at follow-up and were re-interviewed 18 months later (n=1,092), OTS longitudinal study 2005-2009

Quit aid

Sample size

n (%)


(RR)


(CI) P value Model ≥12 months Three groups for NRT use duration, based on the longest use duration at any one follow-up (best fit model) Non-use 1 612 (56.0) 7.0% Referent -------- <8 weeks 383 (35.1) 3.1% 0.45 0.24-0.83 0.012 ≥8 weeks 97 (8.9) 8.3% 1.17 0.57-2.42 0.66 <8 weeks 2 383 (35.1) 3.1% Referent† -------- ≥8 weeks 97 (8.9) 8.3% 2.63 1.11-6.26 0.029 † The model analysis included all three groups for NRT use duration; only the results for using NRT <8 weeks and ≥8 weeks are presented here.

84

The overall adjusted analysis showed that those who used any NRT <8 weeks had a lower

likelihood of long-term abstinence at the end of 18 months of follow-up than those who did not

use any NRT (p = 0.036). Using any NRT ≥8 weeks was associated with a 3 times higher

likelihood of long-term abstinence than using any NRT <8 weeks. There was no difference in

long-term abstinence between using any NRT ≥8 weeks and not using any NRT (Table 18).

Adjusted confounding variables included baseline variables of daily smoking, HSI, quit

intention, self-perceived confidence of quitting, and ever use of NRT, and a follow-up variable

of number of quit attempts. Self-perceived confidence of quitting was associated with a lower

likelihood of quitting. No significant modifying variables were found for the association between

any NRT use duration and long-term abstinence at the end of 18 months of follow-up.

Table 18. Adjusted Poisson regression analysis: association between any NRT use duration and long-term abstinence (continuous quitting ≥12 months) at the end of 18 months of follow-up among baseline smokers who made serious quit attempts at follow-up and were re-interviewed 18 months later (n=1,092), OTS longitudinal study 2005-2009

† Adjusted for baseline variables of daily smoking, HSI, quit intention, self‐perceived confidence of quitting, and ever use of NRT, and a follow‐up variable of number of quit attempts.

‡ The model analysis included all three groups for NRT use dura on; only the results for using NRT <8 weeks and ≥8 weeks are presented here.

Model Quit aid Relative risk (RR)† 95% Confidence Interval (CI) P value Three groups for NRT use duration, based on the longest use duration at any one follow-up (best fit model) 1 Non-use Referent -------- <8 weeks 0.47 0.23-0.95 0.036 ≥8 weeks 1.41 0.62-3.17 0.41 2 <8 weeks Referent‡ -------- ≥8 weeks 3.02 1.29-7.08 0.011

85

7.2.2 By patch use duration

The difference in QIC values showed that the Poisson model was best fitted by patch use

duration with three categories (i.e., non-use, use <8 weeks, and use ≥8 weeks, based on the

longest use duration at any one follow-up). The proportion of long-term abstinence at the end of

18 months of follow-up was 6%, 3%, and 13% for not using patches, using patches <8 weeks,

and using patches ≥8 weeks, respectively. The crude analysis showed that those who used

patches ≥8 weeks were 2 times more likely to quit ≥12 months than those who did not use

patches (borderline significance, p=0.058) and 4 times more likely to quit ≥12 months than those

who used patches <8 weeks. Using patches < 8 weeks was associated with a lower likelihood of

long-term abstinence than not using patches (borderline significance, p = 0.079) (Table 19).

Table 19. Crude Poisson regression analysis: association between nicotine patch use duration and long-term abstinence (continuous quitting ≥12 months) at the end of 18 months of follow-up among baseline smokers who made serious quit attempts at follow-up and were re-interviewed 18 months later (n=1,092), OTS longitudinal study 2005-2009

Quit aid

Sample size

n (%)


(RR)


(CI) P value Model ≥12 months Three groups for patch use duration, based on the longest use duration at any one follow-up (best fit model) Non-use 1 805 (73.7) 6.1% Referent -------- <8 weeks 231 (21.2) 3.0% 0.50 0.23-1.08 0.079 ≥8 weeks 56 (5.1) 12.5% 2.05 0.98-4.32 0.058 <8 weeks 2 231 (21.2) 3.0% Referent† -------- ≥8 weeks 56 (5.1) 12.5% 4.13 1.51-11.28 0.0058 † The model analysis included all three groups for patch use duration; only the results for using patches <8 weeks and ≥8 weeks are presented here.

86

The overall adjusted analysis showed that using patches ≥8 weeks were associated with a 2.6

times higher likelihood of long-term abstinence than not using patches and 4.7 times higher

likelihood of long-term abstinence than using patches <8 weeks at the end of 18 months of

follow-up (Table 20). Confounders adjusted for in this model included baseline variables of daily

smoking, HSI, intention to quit, self-perceived confidence of quitting, and workplace smoking

ban, and follow-up variables of using NRT without patches and number of quit attempts. Using

NRT other than patches at follow-up and self-perceived confidence of quitting had a lower

likelihood of quitting than their counterparts. No significant modifying variables were found.

Table 20. Adjusted Poisson regression analysis: association between nicotine patch use duration and long-term abstinence (continuous quitting ≥12 months) at the end of 18 months of follow-up among baseline smokers who made serious quit attempts at follow-up and were re-interviewed 18 months later (n=1,092), OTS longitudinal study 2005-2009

† Adjusted for baseline variables of daily smoking, HSI, intention to quit, self‐perceived confidence of quitting, and workplace smoking ban, and follow‐up variables of using NRT without patches and number of quit attempts.


Model Quit aid Relative risk (RR)† 95% Confidence Interval (CI) P value Three groups for patch use duration, based on the longest use duration at any one follow-up (best fit model) 1 Non-use Referent -------- <8 weeks 0.57 0.26-1.26 0.17 ≥8 weeks 2.62 1.25-5.50 0.011 2 <8 weeks Referent‡ -------- ≥8 weeks 4.57 1.73-12.05 0.0021

87

7.2.3 By gum use duration

The difference in QIC values showed that the Poisson model was best fitted by gum use duration

with three categories (i.e., non-use, use <8 weeks, and use ≥8 weeks, based on the longest use

duration at any one follow-up). The proportion of long-term abstinence at the end of 18 months

of follow-up was 7%, 2%, and 3% for not using gum, using gum <8 weeks, and using gum ≥8

weeks, respectively. The crude analysis showed that those who used gum <8 weeks were 71%

less likely to quit ≥12 months at the end of 18 months of follow-up than those who did not use

gum. Using gum ≥8 weeks was not associated with long-term abstinence at the end of 18 months

of follow-up, compared to not using gum or using gum <8 weeks (Table 21).

Table 21. Crude Poisson regression analysis: association between nicotine gum use duration and long-term abstinence (continuous quitting ≥12 months) at the end of 18 months of follow-up among baseline smokers who made serious quit attempts at follow-up and were re-interviewed 18 months later (n=1,092), OTS longitudinal study 2005-2009

Quit aid

Sample size

n (%)


(RR)


(CI) P value Model ≥12 months

Three groups for gum use duration, based on the longest use duration at any one follow-up (best fit model)Non-use 1 858 (78.6) 6.8% Referent -------- <8 weeks 201 (18.4) 2.0% 0.29 0.11-0.80 0.017 ≥8 weeks 33 (3.0) 3.0% 0.45 0.06-3.14 0.42 <8 weeks 2 201 (18.4) 2.0% Referent† -------- ≥8 weeks 33 (3.0) 3.0% 1.52 0.18-13.21 0.70 † The model analysis included all three groups for gum use duration; only the results for using gum <8 weeks and ≥8 weeks are presented here.

88

The overall adjusted analysis showed that those who used gum <8 weeks were 66% less likely to

quit ≥12 months at the end of 18 months of follow-up than those who did not use gum. Using

gum ≥8 weeks was not associated with long-term abstinence, compared to not using gum or

using gum <8 weeks (Table 22). Confounding variables included baseline variables of daily

smoking, HSI, making a quit attempt in the last 12 months prior to baseline, self-perceived

confidence of quitting, and perception of quitting medications making quit easier, and a follow-

up variable of number of quit attempts. Self-perceived confidence of quitting (yes vs. no) was

associated with a lower likelihood of quitting. No significant modifying variables were found for

the association between gum use duration and quit ≥12 months at the end of 18 months of

follow-up.

Table 22. Adjusted Poisson regression analysis: association between nicotine gum use duration and long-term abstinence (continuous quitting ≥12 months) at the end of 18 months of follow-up among baseline smokers who made serious quit attempts at follow-up and were re-interviewed 18 months later (n=1,092), OTS longitudinal study 2005-2009

† Adjusted for baseline variables of daily smoking, HSI, making a quit attempt in the last 12 months prior to baseline, self‐perceived confidence of quitting, and perception of using quit medications making quit easier, and a follow‐up variable of number of quit attempts.

‡ The model analysis included all three groups for gum use duration; only the results for gum use <8 weeks and ≥8 weeks are presented here.

Model Quit aid Relative risk (RR)† 95% Confidence Interval (CI) P value Three groups for gum use duration, based on the longest use duration at any one follow-up (best fit model) 1 Non-use Referent -------- <8 weeks 0.34 0.12-0.92 0.032 ≥8 weeks 0.56 0.08-3.78 0.55 2 <8 weeks Referent‡ -------- ≥8 weeks 1.67 0.20-13.74 0.63

89

7.3 Short-Term Abstinence (Continuous Quitting ≥1 Month) at Any Period of Follow-Up Based on the difference in QIC values, it was found that non-linearity existed for short-term

abstinence at any period of follow-up by all three quit aid use durations. No overdispersion was

found in the Poisson models for the associations between quit aid use duration (any NRT,

patches, and gum) and short-term abstinence at any period of follow-up. Poisson models with

robust standard errors were applied.


The difference in QIC values showed that the Poisson model was best fitted by any NRT use

duration with five categories (i.e., non-use and use <2, ≥2-<4, ≥4-<6, and ≥6 weeks), based on

the sum of use durations across all follow-ups. For the NRT use duration with three categories

(i.e., non-use, use <8 weeks, and use ≥8 weeks), the model was better fitted by the sum of use

durations than the longest use duration at any one follow-up.

The majority of respondents did not use any NRT (62%), 31% used any NRT <8 weeks, and

only 7% used any NRT for the recommended duration, in relation to short-term abstinence at any

period of follow-up. The proportion of short-term abstinence at any period of follow-up was

52%, 37%, and 71% for not using NRT, using NRT <8 weeks, and using NRT ≥8 weeks,

respectively (Table 23).

For NRT use duration with five categories, the short-term abstinence rate was lower among those

who used any NRT <6 weeks (from 30% to 45%) than those who did not use any NRT, but was

higher among those who used any NRT ≥6 weeks (71%) than those who did not use any NRT

(Table 23).

For any NRT use duration with three categories, the crude analysis showed that those who used

any NRT <8 weeks were 29% less likely to quit ≥1 month at any period of follow-up than those

who did not use any NRT. Those who used any NRT ≥8 weeks were 1.4 times more likely to

90

quit ≥1 month than those who did not use any NRT and 1.9 times more likely to quit ≥1 month

than those who used any NRT <8 weeks at any period of follow-up (Table 23).

For NRT use duration with five categories, the crude analysis showed that using NRT <4 weeks

was associated with a lower likelihood of short-term abstinence at any period of follow-up (41%

less for using <2 weeks and 32% less for using ≥2-<4 weeks) than not using any NRT; using any

NRT ≥4-<6 weeks was not associated with short-term abstinence, compared to not using any

NRT; and using any NRT ≥6 weeks was associated with a higher likelihood of short-term

abstinence at any period of follow-up (1.4 times greater) than not using any NRT (Table 23).

Table 23. Crude Poisson regression analysis: association between any NRT use duration and short-term abstinence (continuous quitting ≥1 month) at any period of follow-up among baseline smokers who made serious quit attempts at follow-up (n=1,590), OTS longitudinal study 2005-2009

Quit aid

Sample size

n (%)


(RR)


(CI) P value Model ≥1 month Three groups for NRT use duration, based on the sum of use durations across all follow-ups Non-use 1 980 (61.6) 51.5% Referent -------- <8 weeks 498 (31.3) 36.8% 0.71 0.63-0.81 <0.0001 ≥8 weeks 112 (7.0) 71.4% 1.39 1.21-1.58 <0.0001 <8 weeks 2 498 (31.3) 1.7% Referent† -------- ≥8 weeks 112 (7.0) 2.4% 1.94 1.65-2.29 <0.0001 Fiver groups for NRT use duration, based on the sum of use durations across all follow-ups (best fit model) Non-use 3 980 (61.6) 51.5% Referent <2 weeks 258 (16.2) 30.2% 0.59 0.48-0.71 <0.0001 ≥2-<4 weeks 129 (8.1) 34.9% 0.68 0.53-0.86 0.0017 ≥4-<6 weeks 73 (4.6) 45.2% 0.88 0.68-1.14 0.32 ≥6 weeks 150 (9.4) 71.3% 1.38 1.23-1.56 <0.0001 † The model analysis included all three groups for NRT use duration; only the results for using NRT <8 weeks and ≥8 weeks are presented here.

For any NRT use duration with three categories, the overall adjusted analysis showed that those

who used any NRT <8 weeks were 17% less likely to quit ≥1 month at any period of follow-up

than those who did not use any NRT. Using any NRT ≥8 weeks was associated with a 1.6 times

higher likelihood of short-term abstinence than not using any NRT and a 1.9 times higher

likelihood of short-term abstinence than using NRT <8 weeks at any period of follow-up (Table

91

24). Confounding variables included baseline variables of daily smoking, number of cigarettes

smoked per day, self-perceived addiction, self-perceived easiness of quitting, self-perceived

confidence of quitting, self-perceived benefit from quitting, home smoking restrictions, and ever

use of NRT, and follow-up variables of using other tobacco products and time in the study. Daily

smoking was associated with a lower likelihood of quitting than non-daily smoking. Self-

perceived addiction as very addicted was associated with a lower likelihood of quitting than

those not very addicted. Self-perceived easiness of quitting was associated with a higher

likelihood of quitting. The longer the time in the study, the higher the likelihood of quitting.

Other confounders were not associated with short-term abstinence at any follow-up.

For any NRT use duration with five categories, the overall adjusted analysis showed that those

who used any NRT <2 weeks were 29% less likely and those who used any NRT ≥2-<4 weeks

were 23% less likely than those who did not use any NRT to quit ≥1 month at any period of

follow-up. Using any NRT ≥4-<6 weeks were not associated with short-term abstinence at any

period of follow-up, compared to not using any NRT. Using any NRT ≥6 weeks was associated

with a 1.6 times higher likelihood of short-term abstinence at any period of follow-up than not

using any NRT (Table 24). Confounders adjusted in this model included the same confounders

as in the model for any NRT use duration with three categories. The confounding effects were

also the same as those in the model for any NRT use duration with three categories. No

significant modifying variables were found for the association between any NRT use duration

(either with three categories or five categories) and short-term abstinence at any period of

follow-up.

92

Table 24. Adjusted Poisson regression analysis: association between any NRT use duration and short-term abstinence (continuous quitting ≥1 month) at any period of follow-up among baseline smokers who made serious quit attempts at follow-up (n=1,590), OTS longitudinal study 2005-2009

† Adjusted for baseline variables of daily smoking, number of cigarettes smoked per day, self‐perceived addiction, self‐perceived easiness of quitting, self‐perceived confidence of quitting, self‐perceived benefit from quitting, home smoking restrictions, and ever use of NRT, and follow‐up variables of using other tobacco products and time in the study for both models (either with three groups or five groups for NRT use duration).




duration with four categories (i.e., non-use and use <4, ≥4-<8, and ≥8 weeks), based on the

longest use duration at any one follow-up before the quitting outcome. For the patch use duration

with three categories (i.e., non-use, use <8 weeks, and use ≥8 weeks), the model was better fitted

by the sum of use durations than the longest use duration at any one follow-up.

For patch use duration with three categories based on the sum of use durations across all follow-

ups before the quitting outcome, 77% of respondents did not use patches, 39% used patches <8

weeks, and 4% used patches for the recommended duration. The proportion of short-term

abstinence at any period of follow-up was 49%, 39%, and 82% for the three patch use groups,

respectively. The crude analysis showed that using patches <8 weeks was associated with a 19%

lower likelihood of short-term abstinence at any period of follow-up than not using patches.

Model Quit aid Relative risk (RR)† 95% Confidence Interval (CI) P value Three groups for NRT use duration, based on the sum of durations across all follow-ups 1 Non-use Referent -------- <8 weeks 0.83 0.72-0.96 0.010 ≥8 weeks 1.61 1.39-1.88 <0.0001 2 <8 weeks Referent‡ -------- ≥8 weeks 1.94 1.64-2.29 <0.0001 Five groups for NRT use duration, based on the sum of durations across all follow-ups (best fit model) 1 Non-use Referent -------- <2 weeks 0.71 0.58-0.86 0.0006 ≥2-<4 weeks 0.77 0.60-0.98 0.036 ≥4-<6 weeks 1.00 0.77-1.29 0.99 ≥6 weeks 1.63 1.42-1.87 <0.0001

93

Using patches ≥8 weeks was associated with a 1.7 times higher likelihood of short-term

abstinence than not using patches and a 2.1 times higher likelihood of short-term abstinence than

using patches <8 weeks (Table 25).

For patch use duration with four categories based on the longest use duration at any one follow-

up before the quitting outcome, 77% did not use patches, 15% used patches <4 weeks, 4% used

patches between ≥4 and <8 weeks, and 4% used patches ≥8 weeks. The proportion of short-term

abstinence at any follow-up was 49%, 33%, 65%, and 83% for the four patch use groups,

respectively. The crude analysis showed that using patches <4 weeks was associated with a 32%

lower likelihood of short-term abstinence at any follow-up, using patches between ≥4 and <8

weeks was associated with a 1.3 times higher likelihood of short-term abstinence at any follow-

up, and using patches ≥8 weeks was associated with a 1.7 times higher likelihood of short-term

abstinence at any follow-up than not using patches.

Table 25. Crude Poisson regression analysis: association between nicotine patch use duration and short-term abstinence (continuous quitting ≥1 month) at any period of follow-up among baseline smokers who made serious quit attempts at follow-up (n=1,590), OTS longitudinal study 2005-2009

Quit aid

Sample size

n (%)


(RR)


(CI) P value Model ≥1 month Three groups for patch use duration, based on the sum of use durations across all follow-ups Non-use 1 1227 (77.2) 48.7% Referent -------- <8 weeks 298 (18.7) 39.3% 0.81 0.69-0.94 0.0054 ≥8 weeks 65 (4.1) 81.5% 1.67 1.47-1.90 <0.0001 <8 weeks 2 298 (18.7) 39.3% Referent† -------- ≥8 weeks 65 (4.1) 81.5% 2.08 1.73-2.49 <0.0001 Four groups for patch use duration, based on the longest use duration at any one follow-up (best fit model) Non-use 1 1227 (77.2) 48.7% Referent <4 weeks 238 (15.0) 33.2% 0.68 0.56-0.82 <0.0001 ≥4-<8 weeks 68 (4.3) 64.7% 1.33 1.10-1.60 0.0026 ≥8 weeks 57 (3.6) 82.5% 1.69 1.48-1.93 <0.0001 † The model analysis included all three groups for patch use duration; only the results for using patches <8 weeks and ≥8 weeks are presented here.

94

For the model with three categories for patch use duration, the overall adjusted analysis showed

that using patches ≥8 weeks was associated with a 2.0 times higher likelihood of short-term

abstinence than not using patches and a 2.1 times higher likelihood of short-term abstinence than

using patches <8 weeks at any period of follow-up. Using patches <8 weeks was not associated

with short-term abstinence at any period of follow-up, compared to not using patches (Table 26).

Adjusted confounders included baseline variables of daily smoking, cigarettes per day smoked,

self-perceived addiction, self-perceived easiness of quitting, self-perceived confidence of

quitting, self-perceived benefit from quitting, home smoking restrictions, ever use of NRT, and

ever use of other quit methods, and follow-up variables of using other quit methods and using

NRT other than patches. Daily smoking was associated with a lower likelihood of quitting than

non-daily smoking. Self-perceived addiction was associated with a lower likelihood of quitting

than their counterparts. Self-perceived easiness of quitting was associated with a higher

likelihood of quitting. Using NRT other than patches <8 weeks was associated with a lower

likelihood of short-term abstinence than not using NRT other than patches. There was no

difference between using NRT other than patches ≥8 weeks and not using NRT other than

patches. Other confounders were not associated with short-term abstinence at any period of

follow-up.

For the model with four categories for patch use duration, the overall adjusted analysis showed

that using patches <4 weeks was associated with a 19% smaller likelihood; using patches

between ≥4 and <8 weeks was associated with a 1.6 times higher likelihood; and using patches

≥8 weeks was associated with a 2.0 times higher likelihood of short-term abstinence at any

period of follow-up, compared to not using patches (Table 26). Adjusted confounders included

the same variables as those in the above model with three groups for patch use duration, with one

additional variable: time in the study. The confounders had similar impacts as those in the above

model as well. The longer the time in the study, the higher the likelihood of short-term

abstinence.

95

Table 26. Adjusted Poisson regression analysis: association between nicotine patch use duration and short-term abstinence (continuous quitting ≥1 month) at any period of follow-up among baseline smokers who made serious quit attempts at follow-up (n=1,590), OTS longitudinal study 2005-2009

† For the model with three categories for patch use duration, adjusted for baseline variables of daily smoking, number of cigarettes smoked per day, self‐perceived addiction, self‐perceived easiness of quitting, self‐perceived confidence of quitting, self‐perceived benefit from quitting, home smoking restrictions, ever use of NRT, and ever use of other quit methods, and follow‐up variables of using other quit methods and using other forms of NRT without patches; for the model with four categories for patch use duration, adjusted for one additional variable: time in the study, apart from the confounders in the model with three categories for patch use duration.


Model Quit aid Relative risk (RR)† 95% Confidence Interval (CI) P value Three groups for patch use duration, based on the sum of durations across all follow-ups 1 Non-use Referent -------- <8 weeks 0.96 0.82-1.13 0.6535 ≥8 weeks 2.02 1.72-2.37 <0.0001 2 <8 weeks Referent‡ -------- ≥8 weeks 2.09 1.73-2.54 <0.0001 Four groups for patch use duration, based on the longest use duration at any one follow-up (best fit model) 1 Non-use Referent -------- <4 weeks 0.81 0.67-0.99 0.0364 ≥4-<8 weeks 1.57 1.29-1.91 <0.0001 ≥8 weeks 1.98 1.68-2.33 <0.0001

96



with three categories (i.e., non-use, use <8 weeks, and use ≥8 weeks), based on the longest use

duration at any one follow-up before the quitting outcome.

At follow-up, 82% of respondents did not use gum, 16% used gum <8 weeks, and 3% used gum

for the recommended duration. The proportion of short-term abstinence at any period of follow-

up was 51%, 34%, and 58% for the three gum use groups, respectively. The crude analysis

showed that using gum <8 weeks was associated with a 33% lower likelihood of short-term

abstinence at any period of follow-up than not using gum. Using gum ≥8 weeks was associated

with a 1.7 times higher likelihood of short-term abstinence than using gum <8 weeks. There was

no difference in short-term abstinence between using gum ≥8 weeks and not using gum (Table

27).

Table 27. Crude Poisson regression analysis: association between nicotine gum use duration and short-term abstinence (continuous quitting ≥1 month) at any period of follow-up among baseline smokers who made serious quit attempts at follow-up (n=1,590), OTS longitudinal study 2005-2009

Quit aid

Sample size

n (%)


(RR)


(CI) P value Model ≥1 month Three groups for gum use duration, based on the longest use durations at any one follow-up (best fit model) Non-use 1 1301 (81.8) 50.7% Referent -------- <8 weeks 249 (15.7) 34.1% 0.67 0.56-0.81 <0.0001 ≥8 weeks 40 (2.5) 57.5% 1.13 0.86-1.49 0.37 <8 weeks 2 249 (15.7) 34.1% Referent† -------- ≥8 weeks 40 (2.5) 57.5% 1.68 1.23-2.32 0.0013 † The model analysis included all three groups for gum use duration; only the results for using gum <8 weeks and ≥8 weeks are presented here.

97

The overall adjusted analysis showed that using gum ≥8 weeks was associated with a 1.6 higher

likelihood of short-term abstinence than using gum <8 weeks; using gum <8 weeks was

associated with a 27% lower likelihood of short-term abstinence than not using gum; and there

was no difference between using gum ≥8 weeks and not using gum in short-term abstinence at

any period of follow-up (Table 28). Adjusted confounders included baseline variables of

education, daily smoking, self-perceived addiction, self-perceived easiness of quitting, self-

perceived confidence of quitting, self-perceived benefit from quitting, and ever use of NRT.

Daily smoking was associated with a lower likelihood of quitting than non-daily smoking. Self-

perceived addiction was associated with a lower likelihood of quitting and self-perceived

easiness of quitting was associated with a higher likelihood of quitting. Other confounders were

not associated with short-term abstinence at any period of follow-up. No significant modifying

variables were found for the association between gum use duration and short-term abstinence at

any period of follow-up.

Table 28. Adjusted Poisson regression analysis: association between nicotine gum use duration and short-term abstinence (continuous quitting ≥1 month) at any period of follow-up among baseline smokers who made serious quit attempts at follow-up (n=1,590), OTS longitudinal study 2005-2009

† Adjusted for baseline variables of education, daily smoking, self‐perceived addiction, self‐perceived easiness of quitting, self‐perceived confidence of quitting, self‐perceived benefit from quitting, and ever use of NRT.


Model Modifier Quit aid Relative risk (RR)† 95% Confidence Interval (CI) P value Three groups for gum use duration, based on the longest use durations at any one follow-up (best fit model)

1 Non-use Referent -------- <8 weeks 0.73 0.61-0.87 0.0006 ≥8 weeks 1.15 0.88-1.51 0.3125

2 <8 weeks Referent‡ -------- ≥8 weeks 1.57 1.15-2.16 0.0048

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7.4 Long-Term Abstinence (Continuous Quitting ≥12 Months) at Any Period of Follow-Up The difference in QIC values showed that non-linearity existed for long-term abstinence at any

period of follow-up by all three quit aid use durations. No overdispersion was found in the

Poisson models for the associations between quit aid use duration (any NRT, patches, and gum)

and long-term abstinence at any period of follow-up. Poisson models with robust standard errors

were applied.


The difference in QIC values showed that the Poisson model was best fitted by NRT use duration


duration at any one follow-up before the quitting outcome. At follow-up, 61% of respondents

did not use any NRT, 33% used any NRT <8 weeks, and 6% used any NRT for the

recommended duration, in relation to long-term abstinence during any period of follow-up. The

proportion of long-term abstinence was 6%, 3%, and 12% for not using NRT, using NRT <8

weeks, and using NRT ≥8 weeks, respectively. The crude analysis showed that those who used

any NRT <8 weeks were 46% less likely than those who did not use any NRT to quit ≥12

months at any period of follow-up. Those who used any NRT ≥8 weeks were 1.9 times more

likely than those who did not use any NRT and 3.4 times more likely than those who used any

NRT <8 weeks to quit ≥12 months at any period of follow-up (Table 29).

Table 29. Crude Poisson regression analysis: association between any NRT use duration and long-term abstinence (continuous quitting ≥12 months) at any period of follow-up among baseline smokers who made serious quit attempts at follow-up (n=1,314), OTS longitudinal study 2005-2009

Quit aid

Sample size

n (%)


(RR)


(CI) P value Model ≥12 months Three groups for NRT use duration, based on the longest use durations at any one follow-up (best fit model) Non-use 1 798 (60.7) 6.4% Referent -------- <8 weeks 432 (32.9) 3.5% 0.54 0.31-0.95 0.034 ≥8 weeks 84 (6.4) 11.9% 1.86 0.98-3.53 0.057 <8 weeks 2 432 (32.9) 3.5% Referent† -------- ≥8 weeks 84 (6.4) 11.9% 3.43 1.60-7.37 0.0016 † The model analysis included all three groups for NRT use duration; only the results for using NRT <8 weeks and ≥8 weeks are presented here.

99

The overall adjusted analysis showed that those who used any NRT ≥8 weeks were 2.4 times

more likely than those who did not use any NRT and 4.1 times more likely than those who used

any NRT <8 weeks to quit ≥12 months at any period of follow-up. There was no difference in

long-term abstinence between using any NRT <8 weeks and not using any NRT (Table 30).

Confounding variables included baseline variables of daily smoking, number of cigarettes

smoked per day, HSI, quit intention, self-perceived addiction, self-perceived confidence of

quitting, and having a main reason of quitting for reducing disease risk/improving health, and a

follow-up variable of number of quit attempts. No confounders were associated with short-term

abstinence and no significant modifying variables were found.

Table 30. Adjusted Poisson regression analysis: association between any NRT use duration and long-term abstinence (continuous quitting ≥12 months) at any period of follow-up among baseline smokers who made serious quit attempts at follow-up (n=1,314), OTS longitudinal study 2005-2009

† Adjusted for baseline variables of daily smoking, number of cigarettes smoked per day, HSI, quit intention, self‐perceived addiction, self‐perceived confidence of quitting, and having a main reason to quit smoking for reducing disease risk/improving health, and a follow‐up variable of number of quit attempts


Model Quit aid Relative risk (RR)† 95% Confidence Interval (CI) P value NRT use duration with three categories, based on the longest use durations at any one follow-up (best fit model)



100



duration with three categories (i.e., non-use, use <8 weeks, and use ≥8 weeks), based on the

longest use duration at any one follow-up.

At follow-up, 77% of respondents did not use patches, 20% used patches <8 weeks, and only 4%

used patches for the recommended duration, in relation to long-term abstinence at any period of

follow-up. The proportion of long-term abstinence was 6%, 4%, and 16% for not using patches,

using patches <8 weeks, and using patches ≥8 weeks, respectively. The crude analysis showed

that those who used patches ≥8 weeks were 2.8 times more likely than those who did not use

patches and 4.7 times more likely than those who used patches <8 weeks to quit ≥12 months at

any period of follow-up. There was no difference in long-term abstinence between using patches

<8 weeks and not using patches (Table 31).

Table 31. Crude Poisson regression analysis: association between nicotine patch use duration and long-term abstinence (continuous quitting ≥12 months) at any period of follow-up among baseline smokers who made serious quit attempts at follow-up (n=1,314), OTS longitudinal study 2005-2009

Quit aid

Sample size

n (%)


(RR)


(CI) P value Model ≥12 months Patch use duration with three categories, based on the longest use durations at any one follow-up (best fit model) Non-use 1 1007 (76.6) 5.9% Referent -------- <8 weeks 258 (19.6) 3.5% 0.60 0.30-1.18 0.14 ≥8 weeks 49 (3.7) 16.3% 2.79 1.41-5.50 0.0032 <8 weeks 2 258 (19.6) 3.5% Referent† -------- ≥8 weeks 49 (3.7) 16.3% 4.68 1.90-11.54 0.0008 † The model analysis included all three groups for patch use duration; only the results for using patches <8 weeks and ≥8 weeks are presented here.

101

The overall adjusted analysis showed that those who used patches ≥8 weeks were 3.7 times more

likely than those who did not use patches and 5.5 times more likely than those who used patches

<8 weeks to quit ≥12 months at any period of follow-up. There was no difference in long-term

abstinence between using patches <8 weeks and not using patches (Table 32). Confounding

variables included baseline variables of daily smoking, HSI, intention to quit, setting a quit date,

self-perceived addiction, self-perceived confidence of quitting, and home smoking restrictions,

and a follow-up variable of number of quit attempts. Having tried to quit in the last 12 months

prior to baseline was associated with a lower likelihood of quitting. Other confounders were not

associated with the quitting outcome. No significant modifying variables were found for the

association between patch use duration and long-term abstinence at any period of follow-up.

Table 32. Adjusted Poisson regression analysis: association between nicotine patch use duration and long-term abstinence (continuous quitting ≥12 months) at any period of follow-up among baseline smokers who made serious quit attempts at follow-up (n=1,314), OTS longitudinal study 2005-2009

† Adjusted for baseline variables of daily smoking, HSI, intention to quit, setting a quit date, self‐perceived addiction, self‐perceived confidence of quitting, and home smoking restrictions, and a follow‐up variable of number of quit attempts.


Model Quit aid Relative risk (RR)† 95% Confidence Interval (CI) P value Patch use duration with three categories, based on the longest use durations at any one follow-up (best fit model) 1 Non-use Referent -------- <8 weeks 0.68 0.34-1.36 0.27 ≥8 weeks 3.72 1.85-7.49 0.0002 2 <8 weeks Referent‡ -------- ≥8 weeks 5.51 2.28-13.29 0.0001

102




duration at any one follow-up.

At follow-up, 81% of respondents did not use gum, 16% used gum <8 weeks, and only 3% used

gum for the recommended duration, in relation to long-term abstinence at any period of follow-

up. The proportion of long-term abstinence was 6%, 3%, and 6% for not using gum, using gum

<8 weeks, and using gum ≥8 weeks, respectively. The crude analysis showed that those who

used gum <8 weeks were 62% less likely than those who did not use gum to quit ≥12 months

(p<0.05). There were no differences in long-term abstinence between using gum ≥8 weeks and

using gum <8 weeks, and between using gum ≥8 weeks and not using gum (Table 33).

Table 33. Crude Poisson regression analysis: association between nicotine gum use duration and long-term abstinence (continuous quitting ≥12 months) at any period of follow-up among baseline smokers who made serious quit attempts at follow-up (n=1,314), OTS longitudinal study 2005-2009

Quit aid

Sample size

n (%)


(RR)


(CI) P value Model ≥12 months Gum use duration with three categories, based on the longest use duration at any one follow-up (best fit model) Non-use 1 1067 (81.2) 6.4% Referent -------- <8 weeks 214 (16.3) 2.8% 0.38 0.16-0.93 0.035 ≥8 weeks 33 (2.5) 6.1% 1.33 0.44-4.05 0.61 <8 weeks 2 214 (16.3) 2.8% Referent† -------- ≥8 weeks 33 (2.5) 6.1% 3.66 0.79-16.63 0.097 † The model analysis included all three groups for gum use duration; only the results for using gum <8 weeks and ≥8 weeks are presented here.

103

The overall adjusted analysis showed that there were no differences between using gum <8

weeks and not using gum and between using gum ≥8 weeks and not using gum in long-term

abstinence at any period of follow-up. Using gum ≥8 weeks was associated with a marginally

significant higher likelihood of long-term abstinence (RR=4.3, p=0.059) than using gum <8

weeks (Table 34). Confounding variables included baseline variables of daily smoking, HSI,

intention to quit, having tried to quit in the last 12 months prior to baseline, self-perceived

addiction, and self-perceived confidence of quitting, and a follow-up variable of number of quit

attempts. Having tried to quit in the last 12 months prior to baseline was associated with a

smaller likelihood of quitting. Other confounders were not associated with long-term abstinence.

No significant modifying variables were found for the association between patch use duration

and long-term abstinence at any period of follow-up.

Table 34. Adjusted Poisson regression analysis: association between nicotine gum use duration and long-term abstinence (continuous quitting ≥12 months) at any period of follow-up among baseline smokers who made serious quit attempts at follow-up (n=1,314), OTS longitudinal study 2005-2009

† Adjusted for baseline variables of daily smoking, HSI, intention to quit, having tried to quit in last 12 months prior to baseline, self‐perceived addiction, and self‐perceived confidence of quitting, and a follow‐up variable of number of quit attempts.


Model Quit aid Relative risk (RR)† 95% Confidence Interval (CI) P value Gum use duration with three categories, based on the longest use duration at any one follow-up (best fit model)



104

7.5 Summary of the Association between NRT Use Duration and Smoking Cessation In this study, two quitting outcomes and two time periods were used. The two quitting outcomes

included short-term abstinence (continuous quitting ≥1 month) and long-term abstinence

(continuous quitting ≥12 months). The two time periods for the quitting outcomes included 1) at

the end of 18 months of follow-up (sustainable outcome); and 2) during any period of follow-up

(i.e., the longest abstinence during any period of follow-up, but might relapse at the end of 18

months of follow-up).

At the end of 18 months of follow-up, the eligible sample for the short-term quitting outcome

included baseline current smokers who made at least one serious quit attempt at follow-ups one,

two or/and three (at least six months of follow-up after making a serious quit attempt; n=1,590)

and were re-interviewed at the end of 18 months of follow-up (n=1,368; retention rate=86%).

For the long-term quitting outcome, the eligible sample included baseline current smokers who

made at least one serious quit attempt at follow-ups one or/and two (at least 12 months of follow-

up after making a serious quit attempt; n=1,314) and were re-interviewed at the end of 18 months

of follow-up (n=1,092; retention rate=83%).

During any period of follow-up, the eligible sample for the short-term quitting outcome included

baseline current smokers who made at least one serious quit attempt at follow-ups one, two

or/and three (n=1,590). For the long-term quitting outcome, the eligible sample included

baseline current smokers who made at least one serious quit attempt at follow-ups one or/and

two (n=1,314).

The majority of smokers did not use any NRT (56%-62%), patches (75%-77%), or gum (80%-

82%) for different quitting outcomes when attempting to quit smoking. Only a small proportion

of smokers used these quit aids for the recommended duration (≥8 weeks) (using any NRT: 6%-

9%; using patches: 4%-5%; and using gum: 3%). The crude short-term abstinence rates were

higher than long-term abstinence rates. The crude short-term abstinence rates were much higher

during any period of follow-up than at the end of 18 months of follow-up (i.e., not sustainable).

105

The crude long-term abstinence rates between the two time periods were comparable. Generally,

the crude abstinence rates were highest among those who used patches ≥8 weeks and lowest

among those who used gum <8 weeks (Table 35).

Table 35. Crude quit rate by NRT quit aid use duration, OTS longitudinal study 2005-2009

Short-term abstinence (≥1 month) Long-term abstinence (≥12 months) Quit aid Sample size

N (%) Quit rate

N (%) Sample size

N (%) Quit rate

N (%) At the end of 18 months of follow-up Any NRT Non-use 790 (57.8) 229 (29.0) 612 (56.0) 44 (7.0) <8 weeks 464 (33.9) 91 (19.6) 383 (35.1) 12 (3.1) ≥8 weeks 114 (8.3) 33 (29.0) 97 (8.9) 8 (8.3) Patches Non-use 1023 (74.8) 277 (27.1) 805 (73.7) 50 (6.1) <8 weeks 281 (20.5) 54 (19.2) 231 (21.2) 7 (3.0) ≥8 weeks 64 (4.7) 22 (34.4) 56 (5.1) 7 (12.5) Gum Non-use 1088 (79.5) 294 (27.0) 858 (78.6) 58 (6.8) <8 weeks 239 (17.5) 46 (19.3) 201 (18.4) 4 (2.0) ≥8 weeks 41 (3.0) 13 (31.7) 33 (3.0) 1 (3.0) During any period of follow-up Any NRT Non-use 980 (61.6) 505 (51.5) 798 (60.7) 51 (6.4) <8 weeks 498 (31.3) 183 (36.8) 432 (32.9) 15 (3.5) ≥8 weeks 112 (7.0) 80 (71.4) 84 (6.4) 10 (11.9) Patches Non-use 1227 (77.2) 598 (48.7) 1007 (76.6) 59 (5.9) <8 weeks 298 (18.7) 117 (39.3) 258 (19.6) 9 (3.5) ≥8 weeks 65 (4.1) 53 (81.5) 49 (3.7) 8 (16.3) Gum Non-use 1301 (81.8) 660 (50.7) 1067 (81.2) 68 (6.4) <8 weeks 249 (15.7) 85 (34.1) 214 (16.3) 6 (2.8) ≥8 weeks 40 (2.5) 23 (57.5) 33 (2.5) 2 (6.1)

106

Consistently, there was a “J” shape of associations between quit aid use duration and categorical

quitting outcomes (Figure 3), except for the association between gum use and long-term

abstinence at the end of 18 months of follow-up. In general, using a quit aid <8 weeks was

associated with a smaller likelihood of quitting and using a quit aid ≥8 weeks was associated

with a higher likelihood of quitting than not using them, at the end of 18 months of follow-up.

However, only using patches ≥8 weeks was associated with sustained abstinence at the end of 18

months of follow-up (i.e., p<0.05). Using patches for the recommended duration (≥8 weeks) was

associated with a higher likelihood of short- and long-term abstinence than using any NRT or

gum ≥8 weeks. Using patches for the recommended duration (≥8 weeks) was associated with a

higher likelihood of long-term abstinence than short-term abstinence.

During any period of follow-up, using any NRT ≥6 weeks and using patches ≥4 weeks were

associated with a higher likelihood of short-term abstinence (quitting ≥1 month) and using any

NRT or patches ≥8 weeks was associated with a higher likelihood of long-term abstinence

(quitting ≥12 months) than not using them, but using gum even ≥8 weeks was not associated

with either short- or long-term abstinence. There was a “dose-response” relationship between

any NRT use duration and adjusted RR among NRT users, and between patch use duration and

adjusted RR among patch users for short-term abstinence. Similar to the findings observed at the

end of 18 months of follow-up, using patches for the recommended duration (≥8 weeks) was

associated with a higher likelihood of short- and long-term abstinence than using any NRT or

gum ≥8 weeks. Using patches for the recommended duration (≥8 weeks) was associated with a

higher likelihood of long-term abstinence than short-term abstinence. It is worth noting that

using any NRT ≥8 weeks was associated with a higher likelihood of long-term abstinence

(Figure 3).

Please note that the model fit tests showed that non-linearity existed for all associations between

NRT quit aid use duration and quitting outcomes (i.e., the cessation outcomes should not be

examined by a continuous variable of NRT quit aid use duration). For some associations between

NRT quit aid use duration and short-term quitting outcomes, more than three groups for quit aid

use duration were used, because these categories fit the model best.

107

Short- and long-term quitting outcomes by quit aid use duration, at the end of 18 months of follow-up

Short- and long-term quitting outcomes by quit aid use duration, during any period of follow-up

1 0.74

1.28 1.32

0.0

0.5

1.0

1.5

2.0

non‐use <4 wks ≥4‐<8 wks

≥8 wks

ARR

Any NRT and quitting ≥1 month

(p<.05)

1 0.88

1.74

0.0

0.5

1.0

1.5

2.0

non‐use <8 wks ≥8 wks

ARR

Patch use and quitting ≥1 month

(p<.01)

1 0.83

1.19

0.0

0.5

1.0

1.5

2.0


ARR

Gum use and quitting ≥1 month

1 0.47

1.41

0.0

1.0

2.0

3.0

4.0


ARR

Any NRT and quitting ≥12 months

(p<.05)

1 0.57

2.62

0.0

1.0

2.0

3.0

4.0


ARR

Patch use and quitting ≥12 months

(p=.01)

1

0.34 0.56

0.0

1.0

2.0

3.0

4.0


ARR

Gum use and quitting ≥12 months

(p<.05)

1

0.71 0.77 1

1.63

0.0

0.5

1.0

1.5

2.0


≥4‐<6 wks

≥6 wks

ARR


(p<.001) (p<.05)

(p<.0001)

1 0.81

1.57

1.98

0.0

0.5

1.0

1.5

2.0


≥8 wks

ARR


(p<.0001)

(p<.0001)

(P<.05)

1

0.73

1.15

0.0

0.5

1.0

1.5

2.0


ARR


(p<.001)

1 0.60

2.44

0.0

1.0

2.0

3.0

4.0


ARR

Any NRT and quitting ≥12 months

(p<.01)

1 0.68

3.72

0.0

1.0

2.0

3.0

4.0


ARR

Patch use and quitting ≥12 months

(p<.001)

1

0.46

1.38

0.0

1.0

2.0

3.0

4.0


ARR

Gum use and quitting ≥12 months

Figure 3. Summary of findings of short- and long-term quitting outcomes by quit aid use duration, main analysis (note: ARR=adjusted relative risk)

108

Chapter 8: Summary of the Sensitivity Analysis

To test whether the association between NRT use duration and smoking cessation would be

weakened among smokers who either made a serious quit attempt or reduced smoking but did

not make a serious quit attempt, a sensitivity analysis was conducted. In the sensitivity analysis,

smokers who reduced smoking but did not make any serious quit attempt at follow-up were

included (n = 910 for the quitting outcome at the end of 18 months of follow-up), in addition to

those who made a serious quit attempt at follow-up (n = 1,368 for the quitting outcome at the end

of 18 months of follow-up). In the descriptive analysis of the sensitivity analysis, two quitting

outcomes and two time periods were used, including short-term abstinence (continuous quitting

≥1 month) and long-term abstinence (continuous quitting ≥12 months). The two time periods for

the quitting outcomes included 1) at the end of 18 months of follow-up (sustainable outcome);

and 2) during any period of follow-up (i.e., the longest abstinence during any period of follow-

up, but might relapse at the end of 18 months of follow-up).

At the end of 18 months of follow-up, the eligible sample for the short-term quitting outcome

included baseline current smokers who made at least one serious quit attempt or reduced

smoking at follow-ups one, two or/and three (n=2,695) and were re-interviewed at the end of 18

months of follow-up (at least six months of follow-up after making serious quit attempts;

n=2,278; retention rate=85%). For the long-term quitting outcome, the eligible sample included

baseline current smokers who made at least one serious quit attempt or reduced smoking at

follow-ups one or/and two (n=2,409) and were re-interviewed at the end of 18 months of follow-

up (at least 12 months of follow-up after making serious quit attempts; n=1,992; retention

rate=83%).

During any period of follow-up, the eligible sample for the short-term quitting outcome included

baseline current smokers who made at least one serious quit attempt or reduced smoking at

follow-ups one, two or/and three (at least six months of follow-up; n=2,695). For the long-term

109

quitting outcome, the eligible sample included baseline current smokers who made at least one

serious quit attempt or reduced smoking at follow-ups one or two (at least 12 months of follow-

up; n=2,409).

Compared to those in the main analysis (i.e., those who made a serious quit attempt at follow-

up), even higher proportions of smokers did not use any NRT (67%-72%), patches (83%-85%),

or gum (83%-86%) for different quitting outcomes when attempting to quit or reducing smoking.

Among those who reduced smoking but did not make any serious quit attempt at follow-up, the

proportion of not using any NRT was much higher, at 84% (768 out of 910). Even smaller

proportions of smokers used these quit aids for the recommended duration (≥8 weeks) (using any

NRT: 5%-6%; using patches: 3%; and using gum: 2%). Similar to the main analysis, the crude

short-term quit rates were higher than long-term quit rates. The crude short-term quit rates were

higher during any period of follow-up than at the end of 18 months of follow-up. The crude long-

term quit rates between the two time periods were comparable. Generally, the crude quit rates

were highest among those who used patches ≥8 weeks and lowest among those who used gum

<8 weeks. Compared to the main analysis, all quit rates were lower in the sensitivity analysis.

The long-term quitters were almost the same quitters as in the main analysis (Table 36).

110

Table 36. Crude quit rate by NRT quit aid use duration in the sensitivity analysis, OTS longitudinal study

Short-term abstinence (≥1 month) Long-term abstinence (≥12 months) Quit aid Sample size

N (%) Quit rate

N (%) Sample size

N (%) Quit rate

N (%) At the end of 18 months of follow-up Any NRT Non-use 1558 (68.4) 246 (15.8) 1327 (66.6) 44 (3.3) <8 weeks 592 (26.0) 93 (15.7) 544 (27.3) 12 (2.2) ≥8 weeks 128 (5.6) 34 (26.6) 121 (6.1) 8 (6.6) Patches Non-use 1888 (82.9) 294 (15.6) 1626 (81.6) 50 (3.1) <8 weeks 321 (14.1) 56 (17.5) 298 (15.0) 7 (2.4) ≥8 weeks 69 (3.0) 23 (33.3) 68 (3.4) 7 (10.3) Gum Non-use 1902 (83.5) 314 (16.5) 1649 (82.8) 59 (3.6) <8 weeks 328 (14.4) 46 (14.0) 298 (15.0) 4 (1.3) ≥8 weeks 48 (2.1) 13 (27.1) 45 (2.3) 1 (2.2) During any period of follow-up Any NRT Non-use 1938 (71.9) 692 (35.7) 1707 (70.9) 53 (3.1) <8 weeks 630 (23.4) 206 (32.7) 594 (24.7) 15 (2.5) ≥8 weeks 127 (4.7) 84 (66.1) 108 (4.5) 10 (9.3) Patches Non-use 2280 (84.6) 802 (35.2) 2018 (83.8) 61 (3.0) <8 weeks 344 (12.8) 125 (36.3) 329 (13.7) 9 (2.7) ≥8 weeks 71 (2.6) 55 (77.5) 62 (2.6) 8 (12.9) Gum Non-use 2311 (85.8) 859 (37.2) 2058 (85.4) 70 (3.4) <8 weeks 334 (12.4) 95 (28.4) 304 (12.6) 6 (2.0) ≥8 weeks 50 (1.9) 28 (56.0) 47 (2.0) 2 (4.3)

Among those who either made serious quit attempts or reduced smoking during follow-up, using

any NRT or patches ≥4 weeks was associated with a higher likelihood of short-term abstinence

(quitting ≥1 month) at both time periods (at the end of 18 months of follow-up and during any

period of follow-up). Using any NRT or patches ≥8 weeks had a higher likelihood of short-term

abstinence (2 times higher for using any NRT and 2.5-2.8 times higher for using patches),

compared to not using them. Using gum even ≥8 weeks was not associated short-term

abstinence. Using gum <4 weeks, however, was associated with a lower likelihood of short-term

abstinence during follow-up (Figure 4).

111

Because the long-term quitters were the same as those in the analysis for those who made a

serious quit attempt (i.e., no long-term quitters were from those who reduced smoking but did

not make serious quit attempts at follow-up), long-term abstinence was not examined in the

sensitivity analysis. Long-term outcomes were not meaningful for this smoker population.

Please note that the model fit tests showed that non-linearity existed for all associations between

NRT quit aid use duration and quitting outcomes (i.e., the cessation outcomes should not be

examined by a continuous variable of NRT quit aid use duration). Three or four groups for quit

aid use duration were used to reflect the best model fit. (Other details can be found in Appendix

10)

Short-term abstinence by quit aid use duration, at the end of 18 months of follow-up

Short-term abstinence by quit aid use duration, during any period of follow-up

Figure 4. Summary of findings of the short-term quitting outcome by quit aid use duration, sensitivity analysis

1.00 1.01

1.68

2.04

0.0

1.0

2.0

3.0


≥8 wks

ARR


(p<.01)

(p<.0001)

1 1.18

1.72

2.78

0.0

1.0

2.0

3.0


≥8 wks

ARR


(p<.05)

(p<.0001)

1.00 0.86 1.14

1.32

0.0

1.0

2.0

3.0


≥8 wks

ARR


1.00 0.89

1.38

2.03

0.0

1.0

2.0

3.0


≥8 wks

ARR


(p<.01)

(p<.0001)

1 0.97

1.84

2.49

0.0

1.0

2.0

3.0


≥8 wks

ARR


(p<.0001)

(p<.0001)

1.00 0.75 0.89

1.29

0.0

1.0

2.0

3.0


≥8 wks

ARR


(p<.01)

(note: ARR=adjusted relative risk)

112

Chapter 9: Discussion

9.1 The Overall Impacts of NRT Use in Smoking Cessation

The current study examined the association between duration of NRT use and smoking cessation

in the general population of smokers. There was a consistent “J” shape of association between

quit aid use duration and smoking cessation, both in short-term and long-term. Using any NRT or

patches alone for the recommended duration was associated with a higher likelihood of short-

term (≥1 month) and long-term (12 months) abstinence than not using or using them for the

suboptimal duration (<8 weeks) during any period of follow-up; using any NRT, patches alone,

or gum alone for the sub-optimal duration (<8 weeks) was associated with a lower likelihood of

short- or long-term abstinence, or was not associated with cessation outcomes, compared to not

using them. Only using nicotine patches for the recommended duration was associated with

short- and long-term abstinence at the end of 18 months of follow-up.

Findings of this study showed that both type and duration of NRT quit aids played important

roles in smoking cessation in the general population. Using nicotine gum even for the

recommended duration (≥8 weeks) was not associated with cessation outcomes (i.e., short- or

long-term abstinence during any period of follow-up or at the end of 18 months of follow-up).

However, using nicotine gum for suboptimal duration (<8 weeks) was associated with a smaller

likelihood of long-term abstinence, compared to not using it. Using any NRT for the

recommended duration increased likelihood of short- and long-term abstinence, compared to not

using it during follow-up, but the increased likelihood of abstinence did not sustain at the end of

18 months of follow-up. Using any NRT <8 weeks was associated with a smaller likelihood of

long-term abstinence compared to not using any NRT, which was likely due to gum use <8

weeks. Using patches for the recommended duration increased the likelihood of both short- and

long-term abstinence at the end of 18 months of follow-up, suggesting that using patches for the

recommended duration should be encouraged to be used by smokers in the general population

when attempting to quit smoking.

113

However, the majority of smokers did not use nicotine patches or used it for the suboptimal

duration when attempting to quit smoking. More efforts are needed to encourage smokers to use

nicotine patches for the recommended duration when attempting to quit.

9.1.1 Impacts of Any NRT in Smoking Cessation

With regard to short- and long-term abstinence at the end of 18 months of follow-up, the

threshold and ceiling effects of using NRT could not be determined, because no significant

association was detected.

With regard to quitting outcomes during any follow-up, there was a “dose-response” association

between any NRT use duration and short-term abstinence: the adjusted RR was 0.71 (P<0.001),

0.77 (p<0.05), 1.00 (p>0.05), and 1.63 (P<0.0001) for using any NRT <2 weeks, ≥2-<4 weeks,

≥4-<6 weeks, and ≥6 weeks, respectively. This meant that using NRT ≥6 weeks had the

threshold effects for the short-term abstinence during any follow-up. For long-term abstinence,

using any NRT ≥8 weeks had the threshold effects. However, ceiling effects could not be

determined because only a small proportion of smokers used NRT beyond 12 weeks.

The RR of 1.63 for using any NRT ≥6 weeks in relation to short-term abstinence during any

period of follow-up in the current study was similar to that reported in the 2009 Cochrane

review54 (RR = 1.58 for any NRT use compared to placebo or non-NRT control for smoking

cessation at six or more months of follow-up). In clinical trials, the majority of participants were

more likely to take the medicine for the recommended duration. However, it should be noted that

the overall effect of any NRT in the Cochrane review might include the mixed quitting outcomes

(e.g., abstinence for 7 days, 30 days, 6 months, and 12 months). The even higher RR of 2.4 for

using any NRT ≥8 weeks in relation to long-term abstinence during any period of follow-up was

similar to that observed in the study168 (RR 2.41, 95% CI 0.80-7.24) by Fiore et al. and the study

by Glavas et al.69 (RR 2.42, 95% CI 1.33-4.39). In Fiore’s study,168 the intervention was nicotine

patches and the outcome was 7-day point prevalence at 6 months of follow-up. In Glavas’ study,

the intervention was nicotine patches and the outcome was abstinence at 6 months. The RR of

114

2.4 was also similar to the meta-analysis by Hughes et al.210 which reported a combined OR of

2.5 (95% CI 1.8-3.6) from four randomised trials comparing over-the counter (OTC) nicotine

patches versus placebo patches. In this meta-analysis, three of the four studies had six months of

follow-up and one 2.5 months. Because the majority (95%) of NRT users in the current study

used either nicotine patches or gum, the impacts of any NRT for short- and long-term abstinence

during any period of follow-up might stem from the impact of nicotine patch use.

A population study by West et al.67 reported that the odds ratio for continuous abstinence for six

months in a multinational cohort of smokers was 2.2 (95% 1.3-3.9) between those using NRT

and not using NRT. But the study did not distinguish the NRT users by duration of NRT use. The

quit rates of the continuous abstinence for 6 months in West’s study67 was from 6.9% to 9.4% in

the NRT group and 3.5% to 4.3% in the group not using NRT. The long-term (≥6 months) quit

rates for OTC NRT was reported between 1% and 11% in 7 studies of Hughes’ meta-analysis.210

In my current study, the quit rate for the continuous abstinence for 12 months was similar to

these ranges: 7.0% for the group not using NRT, 3.1% for the group using NRT <8 weeks, and

8.3% for the group using NRT ≥8 weeks, based on the quitting outcome at the end of 18 months

of follow-up.

Population studies that do not show a positive effect of NRT on smoking cessation (including no

effect or even negative effect) may consist of more smokers who used NRT for suboptimal

duration (i.e., <8 weeks), such as the English population study60 and the California population

study63 (no effect of NRT in cessation after NRT widely available over-the-counter). Another

possible reason is that these studies did not control for tobacco dependence. Perhaps only those

who find it difficult to quit smoking would spend the time and expense in seeking quit aids. This

was the case in the current study that NRT users were more likely to be daily smokers, to smoke

more cigarettes per day, and to have a higher level of HSI. NRT users were also more likely to be

those who were less confident to quit, who perceived that quitting was very hard, and who

perceived themselves as very addicted to cigarette smoking. Without adequately controlling for

these potential confounding variables, it should not be surprising to see that NRT has no effect or

115

even a negative effect on smoking cessation in general population studies. In the current study,

adjusted RRs were almost always larger than the crude RRs. This indicates that smoking

cessation outcomes were confounded by the difference in tobacco dependence variables between

NRT (patch or gum) users and non-users.

The current study found that using NRT ≥6 weeks was associated with a higher likelihood of

short-term abstinence based on the longest continuous quit days at some point of follow-up.

Hughes et al.237 have indicated that the longest duration of abstinence is one of the best, if not the

best, predictor of future success at cessation. Although the absolute quit rate was lower for long-

term abstinence (6% for the group not using NRT, 4% for the group using NRT <8 weeks, and

12% for the group using NRT ≥8 weeks) than that for short-term abstinence at any follow-up

(52% for the group not using NRT, 37% for the group using NRT <8 weeks, and 71% for the

group using NRT ≥8 weeks), the RRs for long-term abstinence was much higher than those for

short-term abstinence between using NRT ≥8 weeks and not using NRT. This might suggest that

NRT was associated with not only increasing quitting but also preventing relapse (i.e., more

smokers stayed quitting long-term among those using NRT ≥8 weeks than those not using NRT).

Taking Hughes’ rationale about the longest duration of abstinence and future cessation success,

findings of the association between any NRT use and quitting outcomes in the current study

suggest that smokers should be encouraged to use NRT for at least six weeks, and that it is better

if they use it for the recommended duration of eight weeks of treatment, when attempting to quit

smoking, while using NRT for less than four weeks and using other tobacco products should be

discouraged.

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9.1.2 Impacts of Nicotine Patches in Smoking Cessation

With regard to quitting outcomes at the end of 18 months of follow-up, using patches ≥8 weeks

was associated with a higher likelihood of quitting short-term (RR=1.74) and long-term

(RR=2.62) compared to not using patches and even higher RRs compared to using patches <8

weeks (RR=1.98 and 4.57, respectively for short- and long-term abstinence). Using patches ≥8

weeks had the threshold effects for short-term and long-term abstinence at the end of 18 months

of follow-up.

With regard to quitting outcomes during any follow-up, using patches ≥8 weeks was associated

with a two times higher likelihood of short-term abstinence and 3.7 – 5.5 times higher likelihood

of long-term abstinence than not using patches and using patches <8 weeks. There was a “dose-

response” association between patch use duration and short-term abstinence: the adjusted RR

was 0.81 (p<0.05), 1.57 (p<0.0001), and 1.98 (p<0.0001) for using patches <4 weeks, ≥4 - <8

weeks, and ≥8 weeks, respectively, compared to not using patches. This meant that using patches

≥4 - <8 weeks had the threshold effect for short-term abstinence at some point of follow-up

based on the longest quit days. For long-term abstinence, using patches ≥8 weeks had the

threshold effects. The ceiling effects could not be determined because only a small proportion of

smokers used patched beyond 12 weeks.

The higher RRs for short-term and long-term abstinence by using patches rather than using any

NRT or gum in the current study are in line with many studies. In the 2009 Cochrane review,54

the combined RR for the comparison between using patches and placebo group was 1.66 (95%

CI 1.63-1.81), which was greater than that for any NRT (RR=1.58, 95% CI 1.50-1.66) or gum

(RR = 1.43, 95% CI 1.33-1.53). Findings in the current study showed a stronger impact of

nicotine patches than the combined effect in these clinical trials. However, several clinical trials

also showed higher RRs, including Ehrsam’s study117 (9 weeks of patches, RR 3.50 for the

continuous quit at 12 months), Paoletti’s study193 (18 weeks of patches, RR 3.75 for the

continuous quit at 12 months), Sachs’ study147 (18 weeks of patches, RR 2.65 for the continuous

quit at 12 months), Tonnesen’s study in 1991156 (12 weeks of patches, RR 3.97 for the

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continuous quit at 12 months), Tonnesen’s study in 2000158 (12 weeks of patches, RR 4.72 for

the continuous quit at 12 months),and Wong’s study87 (12 weeks of patches, RR 3.36 for the

continuous quit at 6 months).

The finding that RR was higher for long-term abstinence than short-term abstinence by using

patches ≥8 weeks in the current study is also in line with the 2009 Cochrane review.54 Among

the 26 trials examining the effect of using patches >8 weeks compared to placebo in the same

Cochrane review,54 18 trials reported the continuous quit at 12 months, and 8 reported the

continuous quit at 6 months. Trials reporting continuous quit at 12 months had a higher

proportion of RR >2 (7 out of 18 trials: 39%) than those reporting continuous quit at 6 months (1

out of 8 trials: 13%). This might suggest that nicotine patches were more effective in preventing

relapse. A recent study49 by Japuntich et al. has indicated that nicotine patches reduce lapse risk

and affect the lapse-relapse transition. Another recent clinical trial238 also indicates that long-

term use of nicotine patches reduces the risk for smoking lapses and increases the likelihood of

recovery to abstinence after a lapse.

These findings suggest that smokers should be encouraged to use nicotine patches for at least

four weeks to help achieve short-term quitting goal (≥1 month at any point of follow-up) and that

it is better if they use it for the recommended duration of eight weeks of treatment to obtain

sustained quitting outcomes (at the end of 18 months of follow-up), when attempting to quit

smoking. Using patches for less than four weeks should be discouraged.

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9.1.3 Impacts of Nicotine Gum in Smoking Cessation

With regard to quitting outcomes at the end of 18 months of follow-up, using gum ≥8 weeks was

not associated with short- or long-term abstinence, compared to not using gum or using gum <8

weeks. Using gum <8 weeks, however, was associated with a lower likelihood of long-term

abstinence (RR = 0.35, p<0.05), but was not associated with short-term abstinence, compared to

not using gum.

With regard to quitting outcomes during any period of follow-up, using gum ≥8 weeks was not

associated with short- or long-term abstinence, although the RR was relatively higher for long-

term abstinence (adjusted RR=1.38, p>0.05), compared to not using gum. Compared to using

gum <8 weeks, using gum ≥8 weeks was associated with a higher likelihood of short-term

abstinence (RR=1.57, p<0.01), and a higher likelihood of long-term abstinence at borderline

significance (RR=4.27, p=0.059). Using gum <8 weeks was associated with a lower likelihood of

short-term abstinence (RR=0.73, p<0.001) and an insignificantly lower likelihood of long-term

abstinence (RR=0.46, p=0.085), compared to not using gum.

The combined RR for gum use in the 2009 Cochrane review54 was 1.43 (95% CI 1.33-1.53),

which was lower than that for nicotine patches (RR 1.66, 95% CI 1.53-1.81). The lower RR for

gum and higher RR for patches in the current study were similar to those in the Cochrane review.

In the current study, the RR was 1.15 – 1.19 for short-term quit, and 0.58 – 1.38 for long-term

quit for the comparison between using gum ≥8 weeks and not using gum. Several clinical trials

reported insignificant effect of gum on smoking cessation, such as Fortmann’s study186 (RR 1.24,

95% CI 0.96-1.60), Gilbert’s study127 (RR 1.21, 95% CI 0.52-2.81), Harackiewicz’s study130 (RR

0.90, 95% CI 0.38, 2.15), Hughes’ study91 in 1990 (RR 0.97, 95% CI 0.40, 2.31), Schneider’s

study149 (RR 0.59, 95% CI 0.07-5.11), and Campbell’s study239 (RR 0.98, 95% CI 0.57-1.69).

Among the 53 trials in the 2009 Cochrane review54 examining the effect of nicotine gum on

smoking cessation, only 14 (26.4%) reported significant outcomes, while 19 out of the 41 trials

(46.3%) examining the effect of nicotine patches reported significant outcomes.

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The threshold and ceiling effects could not be determined for gum use duration, because no

significantly positive association was found for the comparison to not using gum. Findings of

this study suggest that using nicotine gum alone <8 weeks should be discouraged in the general

population.

9.1.4 What Would Occur if NRT Users Were Categorized as Yes and No without

Considering the Use Duration?

The majority of previous population-based studies only categorised NRT users into two groups:

users and non-users. In the current study, I mimicked the analysis in this way. The results

showed that NRT users were less likely to quit smoking than non-NRT users in the crude

analysis, and there was no difference in quitting in the adjusted analysis. There was no difference

in quitting short- or long-term between patch users and non-users. Gum users were less likely to

quit than non-users in the crude analysis and adjusted analyses (see detailed results in Appendix

7). These findings suggest that NRT users, especially gum users, were self-selected and prone to

failure in smoking cessation. If duration of quit aid use was not taken into account, the effect of

appropriate use of these quit aids would be disguised. Secondly, population studies that did not

adequately control for smoking dependence would under-estimate the effect of NRT.

9.1.5 Patterns of Quit Aid Use

With regard to quit aids (any form, including pharmaceutical quit medications, behavioural

support, and other quitting methods, i.e., self-help materials, acupuncture, hypnosis, and laser

therapy) in the current study, the majority (62%) of smokers used some forms of quit aids and

38% did not use any quit aids at follow-up when attempting to quit. The commonly used quit

aids were NRT (41%, with or without other forms of quit aids), other quitting methods (23%,

with or without other forms of quit aids), behavioural support (18%, with or without other forms

of quit aids), and bupropion or varenicline (18%, with or without other forms of quit aids). The

proportion of NRT use in combination with other quit aids was 13% with self-help materials etc.,

10% with behavioural support, and 8% with bupropion or varenicline (see Appendix 8).

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However, during any one follow-up (six months), the combination use of NRT and other quit

aids was very low (<4%) and concurrent use of NRT and other quit aids was even lower (<2%).

With regard to NRT use in the current study, the majority of respondents did not use any NRT

(59%), approximately one third used NRT <8 weeks, and a small proportion (8%) used NRT ≥8

weeks, among those who made at least one serious quit attempt at follow-up. Among NRT users,

the common types of NRT use were patches alone (42%), gum alone (32%), and patches and

gum (11%) (see Appendix 8). This use pattern is consistent with that in a population-based

cohort of smokers in Washington County, Maryland.61 This study61 found that 10% of smokers

used nicotine gum only, 16% used nicotine patches only, and 10% used both gum and patches,

where NRT use was defined as ever use in this study. The small proportion of smokers using

NRT ≥8 weeks in the current study was consistent with a recent study68 where only 7.5% of

recent quitters (33.2% among NRT users) had used NRT >6 weeks.

NRT users were more likely to be daily and heavy smokers with high HSI than non-NRT users

(86% vs. 66% for daily smoking, 29% vs. 15% for smoking 21+ cigarettes/day, and 36% vs.

23% for high HSI). However, NRT users were more likely to make quit attempts in the 12

months prior to baseline (46% vs. 38%) and more likely to plan the most recent quit attempt

(23% vs. 17%) than non-NRT users. NRT users perceived themselves to be more addicted to

cigarette smoking (79% vs. 50%) and less confident in quitting (60% vs. 71%) than non-NRT

users. These findings suggest that NRT users were self-selected: they were heavy smokers with

self-perceived more difficulty and less confidence in quitting, compared to non-NRT users in this

study. NRT users might be prone to failure in quitting, compared to non-NRT users. The

differences between NRT users and non-users in the current study were similar to those in other

population studies. Shaffman et al.240 assessed differences in demographic and smoking

characteristics between smokers who have and have not used NRT. This study240 found that NRT

users (both ever-users and OTC users) were heavier smokers, had experienced more craving and

withdrawal upon quitting, and scored higher on measures of dependence.

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Buck et al.60 investigated smoking and quitting with the aid of NRT in a representative general

adult population in England and found that 17% of current smokers ever used nicotine gum and

15% ever used nicotine patches among those who made cessation attempts, based on the 1995

survey data. No other information on smokers’ characteristics was reported in this study. In the

current study, a much higher proportion (56%) of current smokers ever used NRT. This might be

because of the availability of over the counter NRT since 1996, increasing advertisements about

NRT, and smokers’ willingness using NRT, and partly because of the existence of the Smoking

Treatment for Ontario Patients (STOP) study that has been providing free NRT products since

2006. Pierce et al.63 reported that NRT use among quitters increased 51% (from 9% in 1992 to

14% in 1999) based on the large population-based California Tobacco Surveys.

When comparing those who used NRT <8 weeks and ≥8 weeks, the big difference was age (older

in the group using NRT ≥8 weeks) and home smoking restrictions (37% in the group using NRT

≥8 weeks versus 26% in the group using NRT <8 weeks); all other aspects with regard to socio-

demographic characteristics and tobacco dependence were very similar between these two

groups. This might suggest that the difference in quitting outcomes in these two groups would be

more likely due to the difference in NRT use duration.

The median days of NRT use duration ranged from 9 to 14 (mean ranging from 21.8 to 28 days)

for the 18 months of follow-up in the current study, which was consistent with previous

studies.63, 211, 241 In Pierce’s study,63 the mean duration of NRT use was 29.7 days in 1992, 26.2

days in 1996 and 28.2 days in 1999, and the median use was only 14 days based on data from the

large population-based California Tobacco Surveys. Burns et al.211 reported that the median

duration of NRT use was 9.8 days among those who made quit attempts and used NRT, and 12%

of smokers who made quit attempts used NRT ≥8 weeks. Etter et al.241 found that the median

duration of NRT use was 15 days among ever NRT users. Although the percentage of NRT use

has increased steadily in recent years, the duration of NRT use has stayed the same compared to

10-18 years ago. It is clear that smokers used NRT strikingly below the recommended duration

(8-12 weeks) in the general population (8% among those who made serious quit attempts in the

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current study). The effectiveness of NRT might not be observed in general population studies

due to this small proportion of NRT users who used NRT for the recommended duration.

Burns et al.211 found that younger people (18-44 years old) and those <200% federal poverty

level were more likely to discontinue NRT for reasons other than having stopped smoking (e.g.,

side effects, NRT did not help, and the cost of NRT). In this study,211 family income was not

measured. Balmford et al.242 investigated the prevalence of and reasons for premature

discontinuation of stop-smoking medications. The study242 used the sample of 1,219 smokers or

recent quitters who had used medications in the last year (81% NRT, 20% prescription only),

from the International Tobacco Control (ITC) Four-Country Survey. The study242 found that

most of the sample (69%) discontinued medications use prematurely and this was more common

among NRT users (71%). OTC NRT users were particularly likely to stop using the medications

prematurely (76.3%). The most common reasons for discontinuation of medications were relapse

back to smoking (42%), side effects (18%), and believing that the medications was no longer

needed (17%). The study indicates that importantly, 65.6% who discontinued because they

believed the medications had worked were abstinent. The study242 concluded that premature

discontinuation of stop-smoking medications is common but is not a plausible reason for poorer

quitting outcomes for most people. The current study was consistent with the ITC study.242 The

proportion of smokers using NRT for suboptimal duration was similar among NRT users in the

current study (80%) compared to the ITC Four-Country survey study (76.3% for OTC NRT). In

the current study, using NRT especially nicotine patches for the recommended duration

corresponded to a higher likelihood of smoking cessation than not using NRT, which is in line

with the ITC study242 that a higher proportion of abstainers quit smoking by using NRT until

they quit.

In the current study, it was found that young people (aged 18-29) were less likely to use NRT ≥8

weeks. There was no difference in NRT use duration by education levels. There was no

difference in concern about the side effects of quit medications by NRT use duration in the

current study. However, concern about the cost of quit medications (i.e., difficult to use it due to

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the cost) was associated with use NRT <8 weeks (44%), compared to 35% among those who

used NRT ≥8 weeks. In the current study, those using NRT ≥8 weeks had a higher proportion of

receiving free NRT (7.5%) than those using NRT <8 weeks (5.1%), although the difference was

not statistically significant. It appears that reducing the costs associated with using NRT by

increasing the subsidization of NRT or decreasing the price of NRT would boost NRT use for the

recommended duration, and might enhance the effectiveness of NRT in the general population.

9.2 Findings in the Sensitivity Analysis

In the sensitivity analysis, the associations between NRT quit aids and quitting outcomes were

examined among those who either made a serious quit attempt or reduced smoking at follow-up.

Respondents in the sensitivity analysis were very similar to those in the analysis for those who

made a serious quit attempt. Respondents in both samples smoked the same amount of cigarettes,

made the same number of lifetime quit attempts, and had the same level of perceived addiction,

easiness of quitting, confidence of quitting, and social and environmental support for quitting.

However, there were a lower proportion of low level of HSI and a higher proportion of high level

of HSI in the sensitivity analysis than in the main analysis (i.e., those who made a serious quit

attempt). Smokers were less likely to use NRT or other quit aids in the sensitivity analysis than

in the main analysis. The quit rate was lower in the sensitivity analysis than in the main analysis.

Using any NRT or patches ≥4 and <8 weeks increased short-term abstinence 1.7 times, and using

them ≥8 weeks increased the short-term abstinence 2-3 times, compared to not using them. Using

gum even for the recommended duration was not associated with short-term abstinence. Because

the long-term quitters in the sensitivity analysis were almost the same as in the analysis for those

who made a serious quit attempt, findings about the long-term quitting outcomes were not

meaningful for this smoker population and thus were not reported. This might be because a very

small number of smokers using patches ≥8 weeks were from those who reduced smoking only

(n=5 for the short-term quitting outcome at the end of 18 months of follow-up and n=6 during

any follow-up). Because smoking is a chronic addictive disease, many quit attempts may be

needed to reach the life-long success of cessation. Thus, those who are not ready to quit but

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prefer to reduce smoking should be encouraged to use NRT, especially nicotine patches, for at

least four weeks, and it is better if they use it for the recommended duration (≥8 weeks).

Several studies have examined the role of NRT use in quitting among smokers unmotivated to

quit. Levy et al.243 examined the association between NRT use for purposes other than quitting

smoking (to cut down on smoking or to delay smoking, NSNRT) and subsequent smoking

cessation efforts. The study243 used a population based cohort study of adult smokers with two

years of follow-up. The study found that any past NSNRT to cut down or delay smoking was not

associated with quit smoking at follow-up (OR = 0.73, 95% CI 0.43-1.24 for cutting down, and

OR = 1.22, 95% CI 0.60-2.50 for delaying). The study concluded that use of NRT for reasons

other than quitting smoking has no effect on smoking cessation.

The use of NSNRT in the study by Levy et al. 243 was ever past use, which is different from my

current study (recent use for reducing smoking). The outcome of quitting smoking in Levy’s

study was not clearly defined. It is not clear if the quitting outcome was for a 7-day point

prevalence, 30-day prevalence, or long-term quitting. The duration and type of NRT were not

classified either. If the majority of smokers in Levy’s study used gum rather than patches, its

results would be consistent with my current study that use of gum was not associated with

quitting outcome. In fact, using gum <8 weeks might be associated with a smaller likelihood of

quitting than not using gum (insignificant in my current study).

Findings in my sensitivity analysis are in line with other studies. A double blind, randomized,

placebo-controlled trial244 of nicotine gum with 2-year follow-up by Wennike et al. reported that

nicotine gum achieved significantly higher rates of point prevalence of cessation than placebo at

12 and 24 months (11.2% versus 3.9%, OR = 3.1, 95% CI 1.4-7.2, and 9.3% versus 3.4%, OR =

2.9, 95% CI 1.2-7.1, respectively) among smoker unwilling to quit. The study244 concluded that

nicotine gum promoted cessation in this population of smokers unwilling to quit. In this study,

participants had 9 clinical visits (each lasted 15-30 minutes), and all intervention groups received

moderate behavioural smoking reduction information and the general implications of smoking.

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Treatment was free of charge and provided for ad libitum use for up to 12 months. In my current

sensitivity analysis, nicotine gum was not associated with short- or long-term cessation. This

might be because the majority of smokers in my study did not use nicotine gum long enough

(only a small proportion used gum for 8 weeks or longer). Another difference is that smokers in

my current study did not receive such substantial behavioural support. Although not significant,

there was a trend in my current study that the longer the gum use, the higher the likelihood of

quitting among smokers who want to quit or reduce smoking. If smokers take nicotine gum long

enough (e.g., 6 – 12 months), we may be able to see the significant impact of nicotine gum on

smoking cessation in the general population of smokers.

Carpenter et al. 245 conducted a randomized clinical trial among smokers currently unmotivated

to quit. The smokers were randomized to a practice quit attempt (PQA) alone or to NRT

(lozenges) plus PQA. The study found that NRT was associated with a significantly higher

incidence of any quit attempt (49% vs. 40%; RR=1.2, 95% CI 1.1-1.4) and any 24-hour quit

attempt (43% vs. 34%; RR = 1.3, 95% CI 1.1-1.5), and it was associated with a marginally

significantly higher quit rate (7-day point prevalence) at any time during the study (19% vs. 19%,

RR = 1.3, 95% CI 1.0-1.7), but the 6-month point prevalence abstinence was not significant

between the two comparison groups. In Carpenter’s clinical trial, the type of NRT was lozenges,

the participants received 72 lozenges, and no lozenges were provided beyond the 6-week

intervention period. Apart from NRT, the participants received intensive behavioral support.

Another clinical trial by Kralikova et al.246 evaluated the efficacy of nicotine 4 mg gum or

nicotine 10 mg inhaler in helping smokers to reduce or quit smoking. The study was placebo-

controlled, randomized trial in a ratio of 2:1 (active : placebo), and participants could choose

inhaler or gum after randomization with 6-months of full treatment. The study found that

sustained abstinence rates were 20.2% in the active group and 8.6% in the placebo group

(p=0.009) at 4 months and 18.7% and 8.6% in the two groups at 12 months (p=0.019),

respectively.

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A recent population based cohort study247 by Beard et al. examined whether use of NRT for

smoking reduction (SR) or temporary abstinence (TA) was associated with smoking cessation.

The study used data from the Smoking Toolkit Study, a series of monthly household surveys of

adults aged 16 and older, using a random location sampling design. The study found that NRT

use for SR or TA prospectively predicted attempts to quit smoking (OR = 1.61, 95% CI 1.30-

2.01 for SR and OR = 1.94, 95% CI 1.56-2.38 for TA) and abstinence (OR = 1.51, 95% CI 1.06-

.2.16 for SR and OR = 2.90, 95% CI 1.51-3.34 for TA) at 6-months follow-up.

It is not clear why the RRs observed in my sensitivity analysis were higher than those in the

analysis for those who made a serious quit attempt. One possible reason is that the reference

groups in the sensitivity analysis and in the main analysis were different. In the sensitivity

analysis, those who wanted to reduce smoking but were unmotivated to quit were more likely to

be daily smokers, less likely to intend to quit in the near future, less likely to have home smoking

restrictions, less likely to use other types of quit aids (e.g., bupropion or varenicline, and self-

help materials), and they also made fewer quit attempts at baseline and follow-up, compared to

those who made at least one serious quit attempt at follow-up (data not shown). On the other

hand, there was no difference between the main and sensitivity analyses among smokers who

used patches ≥8 weeks (data not shown). Because smokers in the sensitivity analysis referent

group were less likely to quit than those in the main analysis and smokers who used patches ≥8

weeks were similar in the two analyses, the difference in terms of RR would be larger in the

sensitivity analysis than in the main analysis. Another possibility may be that those who were

unmotivated to quit but wanted to reduce smoking were different from those who made at least a

serious quit attempt at follow-up in my current study in some unobserved variables (e.g., genetic

difference or difference in co-morbidity). Future studies are needed to explore the possible

reasons.

Current smoking cessation interventions are targeted at smokers who are already motivated and

preparing to quit. Findings from my current study and other studies245-247 suggest that NRT,

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especially patches, should be encouraged to be used by all smokers for the recommended

duration, even among those who do not want to quit or quit immediately.

9.3 Why the Likelihood of Abstinence Is Higher among Nicotine Patch Users Than Gum

Users?

The current study found that using nicotine patches ≥8 weeks but not using gum ≥8 weeks was

associated with a higher likelihood of abstinence, compared to not using patches or gum,

especially on the sustained long-term abstinence (i.e., at the end of 18 months of follow-up).

The difference in quit outcomes for patch and gum users may be due to the difference in the

medications and use methods. Nicotine patches are generally used for 16 or 24 hours with greater

percent replacement of nicotine (generally 14-21 mg).45 Nicotine gum is generally used in 2 or 4

mg per piece by oral administration.45 Nicotine gum is usually used to deal with acute cravings,

but under dosing is common due to its aversive taste45 and much of the nicotine being swallowed

instead of being absorbed buccally. Using nicotine gum is more complex than patches: nicotine

gum should be chewed slowly and properly, until feeling tingling; it should be placed in between

the cheek and gum, and be held there until the flavour or tingling wears off; and, the gum should

last for around half an hour.248 Nicotine gum does not provide a constant nicotine supply level. In

contrast, nicotine patches are easy to apply (once a day administration) and provide a constant

nicotine supply level.

The observed difference in quitting outcomes by patch and gum users may be due to the

difference in the percentage of use of the two quit aids in the current study. For the quitting

outcome at the end of 18 months of follow-up, 4.7% of smokers used patches, but only 3.0%

used gum. There were 64 smokers who used patches ≥8 weeks, but only 41 smokers who used

gum ≥8 weeks (about 56% more smokers used patches for the recommended duration than those

used gum). Those who used gum only for eight or more weeks were very similar to those who

used patches only for eight or more weeks: no differences in socio-demographic characteristics

and tobacco dependence variables. There were some differences between these two groups, but

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all in favor of gum users in terms of smoking cessation (e.g., 57.4% vs. 25.9% for the variable of

someone making quitting difficult, 16.9 vs. 15.0 for cigarettes/day smoked, and 29.6% vs. 11.1%

for ever use of behavioral support for those using patches only ≥8 weeks and using gum only ≥8

weeks, respectively; see Appendix 13 for details). Therefore, the difference in smoking cessation

between using gum and patches was more likely due to the method of using these medications

and the effect of the medications.

9.4 Comparison to Recent Studies

A recent study68 by Alpert et al. reported that the odds of relapse were unaffected by use of NRT

for >6 weeks either with (p=0.117) or without (p=0.159) professional counselling. This is the

only published population study that examined the association between NRT use duration and

relapse rate. This study68 used a prospective cohort study design; data were obtained from a

probability sample of 6,739 Massachusetts adults, with an over-sampling of adult smokers,

young adults, and recent quitters (those who quit smoking in the past 2 years). The sample for

analysis was 787 recent quitters prior to wave one (the sample sizes were even smaller for the

main results based on stratified analyses by heavy and light dependent smokers and then by time

since quitting of 2 years, 1year, and 6 months). The baseline response rate was 46%; follow-up

rates were 56% at wave 2 and 68% at wave 3. Generalized linear latent and mixed models

multilevel logistic modelling was performed to account for intra-individual correlation, and all

analyses were conducted with weighting to account for probability of selection and to adjust for

attrition in respective waves.

Alpert et al.’s study is similar to my study in design – population-based prospective

representative cohort of smokers; however, they did not use the recommended duration (≥8

weeks) as a cutoff value to categorize the NRT use groups. In addition, Alpert et al. did not

examine the effect of NRT on smoking cessation by NRT type. Findings from my study show

that using any NRT even for the recommended duration was not associated with smoking

cessation; only using nicotine patches for the recommended duration was associated with short-

and long-term abstinence at the end of 18 months of follow-up. Compared to Alpert et al.’s

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study, my study had higher response (63% versus 46%) and follow-up (83% versus 56%-68%)

rates. Residual confounding effects from inadequately controlling for tobacco dependence might

exist in Alpert et al.’s study: in their stratified analyses of the main results, it appeared that they

did not control for number of cigarettes per day smoked or HSI. Recall bias may be another

potential reason. As indicated by Borland et al.249 in their study, better recall of quit attempts and

stronger addiction to nicotine are two characteristics found more often among smokers using

stop-smoking medications compared with self-quitters in their International Tobacco Control 4-

country cohort study. This recall bias may under-estimate the effect of NRT on smoking

cessation.

Another recent large randomized controlled trial250 (close to 1,300 smokers in each group) also

reported that offering free NRT to standard helpline support had no additional effect on smoking

cessation. One reason for the no-effect given by the study was that support for smoking cessation

in England is available to all smokers either free or at relatively low cost. The other potential

reason not given by the study was that participants were only offered nicotine patches for 21

days, although a second 21 day supply could be offered.

Another recent large study, the Smoking Treatment for Ontario Patient (STOP) Study251 found

that provision of free NRT following a brief telephone intervention is an effective strategy to

reach and assist a large number of smokers making a quit attempt. In the STOP study,251

participants were offered five weeks of free NRT (either patches or gum in participants’

preference in the ratio of 10:4). The 30-day point prevalence of cessation at six months was

17.8% for the intervention and 9.8% for no-intervention cohorts (RR 1.81, 95% CI 1.75-1.87).

Although the STOP study found that using NRT <8 weeks was associated with a higher

likelihood of quitting, the quit outcome was different from my study (30-day prevalence at six-

months in the STOP study, but 18-months of follow-up in my current study). Secondly,

participants were daily smokers who smoked at least 10 cigarettes per day in the STOP study, but

in my current study all smokers were included. NRT does appear to be most beneficial among

moderate-to-heavy smokers (people who smoke ≥15 cigarettes per day).252

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9.5 Methodology Considerations

9.5.1 Potential Impact of Eligibility and Inclusion Criteria for Sample Selection

In this study, those who were baseline current smokers and made a serious quit attempt at follow-

up were eligible to be included in analysis. The serious quit attempt was defined based on the

follow-up question “How many times have you made a serious attempt to quit smoking in the

past 6 months? By serious, we mean that you made a conscious attempt to stay off cigarettes for

good.” Those who answered at least one serious quit attempt were eligible for inclusion. In the

analysis, those who made a serious quit attempt at follow-up one, two, or three were included in

the analysis for short-term abstinence at the end of 18 months of follow-up, with the assumption

that the serious quit attempt was made at the beginning of each follow-up. Using this assumption,

these smokers would have at least six months of follow-up after making a serious quit attempt. In

the analysis of short-term abstinence, those who made a serious quit attempt at follow-up one,

lost to follow-up two, but were re-interviewed at follow-up three, and those who lost to follow-

up one but had follow-up information at follow-ups two and three were included in the analysis.

For analysis of long-term abstinence at the end of 18 months of follow-up, those who made a

serious quit attempt at follow-up one or two were included, as these smokers would have at least

12 months of follow-up after making a serious quit attempt.

Although the analysis was conducted to use as much available information as possible, smokers

would have different opportunities to provide information on quit attempt and use duration of

NRT quit aids. For example, if smokers who made a serious quit attempt at follow-up one and

used NRT for <8 weeks for this attempt, lost to follow-up two (but used NRT ≥8 weeks for the

quit attempt during that period), and quit ≥1 month at the end of 18 months, these smokers’

short-term abstinence would be attributed to using NRT <8 weeks. This would dilute the effect

of using NRT ≥8 weeks on the quitting outcome. For the similar quit attempt and NRT use

patterns, but smokers did not quit ≥1 month at the end of 18 months, these smokers’ short-term

abstinence (i.e., no quitting) would be attributed to using NRT <8 weeks. This would boost the

effect of using NRT ≥8 weeks but dilute the effect of using NRT <8 weeks on the quitting

outcome.

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Another issue for the above inclusion criteria (smokers who made a serious quit attempt at

follow-up one, two or three for short-term abstinence and smokers who made a serious quit

attempt at follow-up one or two for long-term abstinence, assuming the serious quit attempt was

made at the beginning of each follow-up) was that the serious quit attempt might occur at any

time of each follow-up. If the serious quit attempt occurred toward the end of each follow-up,

those who made a serious quit attempt at follow-up two or three would not have enough follow-

up time after making a serious quit attempt for long-term abstinence (at least 12 months), and

those who made a serious quit attempt at follow-up three would not have long enough follow-up

time after making a serious quit attempt for short-term abstinence (at least one month). To deal

with this issue (i.e., not enough follow-up time after making a serious quit attempt), additional

analyses were conducted. For long-term abstinence, the analysis sample was restricted to those

who made a serious quit attempt at follow-up one only and had complete data (having at least 12

months of follow-up after making a serious quit attempt). For short-term abstinence, the analysis

sample was restricted to those who made a serious quit attempt at follow-up one or two with

complete data (having at least one month of follow-up after making a serious quit attempt),

Findings from the additional analyses showed similar results to those in my current analysis (i.e.,

using any NRT, patches, or gum <8 weeks was not associated with short-term abstinence; using

any NRT or gum even for eight or more weeks was not associated with short-term abstinence;

only using patches for eight or more weeks was associated with a higher likelihood of short-term

abstinence: RR = 1.66, 95% CI 1.08-2.54; using any NRT or gum <8 weeks was associated with

a lower likelihood of long-term abstinence: RR=0.51 and 0.33 for using any NRT and gum <8

weeks, respectively; using patches <8 weeks and using any NRT or gum ≥8 weeks was not

associated with long-term abstinence; only using patches ≥8 weeks was associated with a higher

likelihood of long-term abstinence: RR=3.03, 95% CI 1.49-6.16) (Details about these additional

analyses are presented in Appendix 12) . These additional analyses confirmed the findings in my

current study, and suggest that including some smokers who did not have long enough follow-up

time for long-term quitting outcome diluted the association between patch use duration (≥8

weeks) and long-term quitting, while the impact on short-term quitting was minimal.

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9.5.2 Potential Reverse Causality Issues

People may argue that the observed association between using nicotine patches ≥8 weeks and

short- and long-term abstinence was due to reverse causality. In other words, it could be that the

higher quit rates observed among those reporting a longer duration of NRT use are the result of

self-selection, where those who quit and remain smoke-free continue to use their medication

while those who relapse discontinue use.253 This could certainly be the case. However, it

reinforces the fact that smokers need to continue using NRT to remain abstinent. If they stop

using NRT, they are more likely to relapse to smoking.

Another possibility for “reverse causation” is recall bias, which means that those who quit for

longer are more likely to recall using NRT for a longer time than those who quit for a shorter

time or do not quit. If this is the case, I should observe this association for both gum users and

patch users. However, in my study, only using patches ≥8 weeks was associated with a higher

quit rate than those who did not use patches, but using gum ≥8 weeks was not associated with a

higher quit rate than those who did not use gum. Gum and patch users may be somehow different

so that they choose different cessation aids. In my current study, however, I found that gum and

patch users were very similar in socio-demographic and tobacco dependence variables. The only

significant difference between gum and patch users was a socio-environmental factor for quitting

(someone making quitting difficult: 26% for gum users and 57% for patch users, in favour of

gum users for quitting; Table 51 in Appendix 13). Nevertheless, because smokers recalled the

use of NRT duration and quitting outcome every six months, recall bias cannot be ruled out in

my study. However, if longer quitters should recall longer use of NRT, we should observe that

using NRT (patches or gum) < 8 weeks would be associated with a higher likelihood of quitting

than not using them. That is not the case in my study. This suggests that the reverse causality was

less likely to fully explain the findings in my study: using patches but not gum ≥8 weeks was

associated with a higher quit rate, and using NRT or gum <8 weeks was associated with a lower

quit rate than not using them.

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Findings of my study that longer use of patches was associated with a higher likelihood of

quitting than shorter use of patches are in line with a randomized controlled trial.238 In this

double-blind, randomized placebo-controlled trial,238 the authors found that at week 24,

extended therapy (24 weeks of patches) produced higher rates of point-prevalence abstinence

(31.6% vs. 20.3%, OR=1.81, 95% CI 1.23-2.66); extended therapy reduced the risk for lapse

(hazard ratio = 0.77, 95% CI 0.63-0.95); and increased the chances of recovery from lapses

(hazard ratio = 1.47, 95% CI 1.17-1.84). At week 52, extended therapy had higher quit rates for

prolonged abstinence (29.1% vs. 21.3%, OR=1.55, 95% CI 1.05-2.28) compared to standard

duration therapy (8 weeks of patches plus 16 weeks of placebo) although the point prevalence

and continuous abstinence did not differ. The prolonged abstinence referred to sustained

abstinence from the quit date to a follow-up assessment, allowing for a grace period (usually of

about two weeks to allow for slips/lapses) in this study.238

9.5.3 Analytical Decision: Why Poisson Regression Was Used

In my study, the primary outcome was a binary variable, i.e., quitting for at least one month or

for at least 12 months: yes vs. no. Logistic regression is generally used for binary outcomes and

the results from logistic regression are usually reported as odds ratios. There is nothing wrong

with the use of odds ratios for binary outcomes. However, when working with frequent

outcomes, odds ratios can substantially overestimate the relative risk or prevalence ratio.254

Schwartz et al.255 have indicated that several major US news media dramatically overstated the

effects of race and sex on physicians’ referrals for cardiac catheterization: a 7 percent reduction

in the referral rate for Black women was mistakenly reported as 40 percent using odds ratio.

After extensive discussion in much of the literature, a consensus has been reached that the

relative risk is preferred over the odds ratio for most prospective investigations.256

Several alternatives have been recommended to model binary outcomes in terms of relative

risks.254 Barros and Hirakata compared Cox, Poisson, and log-binomial regression against the

standard Mantel-Haenszel estimators.254 They found that unadjusted Cox and Poisson regression

and Poisson regression with scale parameter adjusted by deviance performed worst in terms of

interval estimates. Poisson regression with scale parameter adjusted by chi-square showed

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variable performance depending on the outcome prevalence. Cox and Poisson regression with

robust variance and log-binomial regression provide correct estimates and were a better

alternative for the analysis of cross-sectional studies with binary outcomes than logistic

regression.254 However, log-binomial regression often suffers from convergence problems,

especially when the model deals with continuous covariates.257-260 Poisson regression and Cox

regression are equivalent in estimating log relative risks (i.e., the parameters estimated are the

same) for binary outcomes.261 The Poisson regression model using the robust error estimator has

become a good alternative to the logistic regression model for the analysis of prospective studies

with independent binary outcomes.262 To use Poisson regression with robust variance estimator

method, no extra programming is necessary; it has no difficulty with converging, and it provides

results very similar to those obtained by using the Mantel-Haenszel procedure when the covariate

of interest is categorical.256

In my study, the quit rate for short-term abstinence was very frequent (ranging from 20% to 34%

at the end of 18 months of follow-up and from 34% to 82% during any period of follow-up). In

my adjusted analyses, continuous variables such as age and number of quit attempts were

controlled for. Log-binomial regression with these covariates had convergence issues. Therefore,

Poisson regression with robust estimator was used in my study to estimate relative risks.

Although Poisson and Cox regression are equivalent in terms of estimating relative risks for

binary outcomes, Poisson regression has the advantage over Cox regression of using a command

syntax similar to linear and logistic regressions in standard statistical software.254 An additional

advantage of using Poisson regression is that it allows the modeling of rates even when some

subgroups contain zero observations (whose corresponding rate is zero and the corresponding

log-rate does not exist in the space of real numbers).223

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9.5.4 Reliability of Outcome Measures

Self-report smoking status is usually employed in clinical practice to determine whether patients

are smoking tobacco during and following treatment.263 This is often also the case for general

population studies. In clinical trials, however, researchers use biomarkers (e.g., carbon monoxide

(CO), cotinine in saliva, plasma, and urine) to confirm self-report smoking status. The SRNT

Subcommittee on Biochemical Verification assessed the utility of biomarkers of tobacco use and

cessation and made recommendations for their application in clinical trials in 2001.264 The

committee concluded that the sensitivity and specificity are both around 90% for CO, and 96-

97% sensitivity and 99-100% specificity for plasma or saliva cotinine, respectively, when

distinguishing tobacco use vs. no tobacco use.264 Findings based on population-based studies also

indicate that misreporting rates are generally very low, typically near zero and seldom exceeding

5-9%, when comparing smoking status by self-report and biomarker confirmation.264 A recent

study using representative data for the Canadian population showed no significant difference

between national estimates of smoking prevalence based on self-report versus urinary cotinine

concentration (smoking prevalence based on self-report was 0.3 percentage points lower than

urinary cotinine concentration).265 Nevertheless, future studies may consider using biomarkers to

confirm smoking status and a diary to confirm duration of quitting and NRT use.

The reliability of the questions used to measure the outcomes in the current study was not

confirmed by biomarkers (either CO or cotinine), because no biomarkers were collected in the

OTS study. However, two questions in the OTS study were used to assess the reliability of the

outcome measures. They might not be accurate to assess the reliability of outcome measures, but

were useful to some extent. The agreement between these two questions among all baseline

current smokers was high (Kappa value at 0.986; for details, see Appendix 6). Therefore,

reliability of the questions for the outcomes of smoking status might not be a critical concern in

this study. However, the quit duration could not be reliably confirmed in the current study.

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9.5.5 Reliability of NRT Use Measures

In observational studies, measurement of NRT use is generally based on self-report. There has

not been any study that uses biomarker to confirm NRT use in large population-based

observational studies. Studies with a prospective study design that collect information about

NRT use in the past 3-6 months would have more accurate information on NRT use than those

asking respondents to recall lifetime use or last year use of NRT. Ideally, information on NRT

use based on a diary should be used. Misclassification of NRT use in the current study is not

known. If the misclassification was non-differential, the association between NRT use and

smoking cessation would be attenuated toward null. If the misclassification was differential, the

association could be over or under-estimated. If those who quit were more likely to recall NRT

use (e.g., those who really wanted to quit and thought NRT would be helpful) than those who did

not quit (e.g., those whose expectation about NRT was low, so that they used NRT but forgot

reporting it), the association would be over-estimated. On the other hand, if those who quit were

less likely to recall NRT use than those who did not quit (i.e., those who discontinued NRT use

due to side effect of NRT), the association would be under-estimated. Future studies may

consider collecting information (e.g., a diary to record NRT use on the type, dose, duration, and

frequency for a month or two in a random sample of a general population study and self-reported

NRT use) to validate NRT use to better understand this potential misclassification issue of NRT

use.

Having said that, two questions on patch, gum, inhaler, and lozenge/tablet use, as well as their

use duration in the OTS longitudinal study, were used to measure the reliability of NRT use

measures to some extent. Based on the answers to these two questions of all baseline current

smokers in the OTS longitudinal study, the reliability of NRT measures was high (Kappa value

at 0.988; for details, see Appendix 6). Therefore, reliability of the questions for the NRT measure

based on the use of NRT is not a critical concern in this study. However, the duration of NRT

measure could not be reliably confirmed in this study.

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9.5.6 Potential Issues around Linking NRT Use and A Quit Attempt

In my study, to be eligible, smokers had to make at least one serious quit attempt during follow-

up in the main analysis. During any period of follow-up, if smokers used NRT before the end of

study (18 months), these smokers would be categorized as using NRT (either in the group using

NRT <8 weeks or using NRT ≥8 weeks, depending on the duration of their NRT use). Only those

who did not use any NRT at all during the entire follow-up would be categorized into the non-

NRT use group. The same applied to patch and gum use. Smokers who had made a serious quit

attempt at follow-up one or two and had not used NRT at follow-up one or two, but had used

NRT at follow-up three only would have been included in the NRT use group. This implied that

those smokers might make a serious quit attempt without using NRT but had to use NRT to stay

smoke-free. In another situation, smokers might use NRT to reduce smoking first (e.g. at follow-

up one) and then made a serious quit attempt later (e.g., at follow-up two or three) with or

without using NRT. These smokers would have been categorized as using NRT. A few

studies249-251 have found that using NRT for reducing smoking may lead to smoking cessation.

Therefore, categorizing smokers who used any NRT during entire follow-up period of 18 months

(longest use of NRT within one six-month window) in my study as using NRT is legitimate,

although the use of NRT might not match with the serious quit attempt exactly.

Some studies have linked NRT use to the last quit attempt. This might introduce some biases

about the impact of NRT use. For example, if smokers could have used NRT ≥8 weeks and were

not smoking at follow-ups one and two, lapsed or relapsed at follow-up three briefly and made

another quit attempt (last quit attempt) at follow-up three but used NRT <8 weeks or did not use

NRT for the last attempt. The quitting outcome might be attributed to using NRT <8 weeks or

non-NRT use if only the last quit attempt approach was used. Using NRT ≥8 weeks before the

last quit attempt might build their confidence in quitting, and smokers could successfully quit

smoking even without using NRT again for their last quit attempt. A recent study266 has shown

that smokers who lapsed during weeks 3-5 of treatment were more likely to recover from a lapse

at weeks six (RR=11.0, p<.001) and 10 (RR=3.7, p<.001) if they continued using patches

compared to those using placebo, in a randomized, double blind placebo controlled trial of 21-

mg nicotine patches. Shiffman and colleagues48 also found that continuing to wear active

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nicotine patch following an initial lapse reduced the odds of progression to full relapse 5-fold,

compared to wearing a placebo patch. Although the studies assessed the impact of continuing

wearing patches, the study266 did mention that they could not be sure if patients who lapsed in

either group actually continued with patch treatment post lapse. Perhaps nicotine patches may

help smokers recover from a lapse by extinguishing the learned reinforcement from smoking.238

On the other hand, smokers might have used NRT quit aids ≥8 weeks for the serious quit attempt

at follow-up one, but did not use any NRT quit aids for the serious quit attempt at follow-up

three, and these smokers did not quit smoking at the end of 18 months of follow-up. Using the

last quit attempt approach, the non-quitting outcome at the end of 18 months would be attributed

to non-use of NRT quit aids although these smokers had used NRT ≥8 weeks at follow-up one.

9.5.7 Handling Missing Data

Missing data in observational studies, especially longitudinal studies is often unavoidable.267 To

deal with missing data, multiple imputation techniques have been recommended as a useful

strategy.268-270 However, this technique can introduce more bias than it solves, and it requires

missing at random (i.e., what caused the data to be missing does not depend upon the missing

data itself).271-274 A recent study274 has indicated that multiple imputation can be useful if

covariates required for confounding adjustment are missing, but the benefits are likely to be

minimal when data are missing in the exposure variable of interest. This study274 also indicated

that multiple imputation can become unreliable and introduce bias not present in a complete case

analysis when there are large amounts of missingness. Missing in my study was mainly due to

lost to follow-up, thus information on the exposure variable of interest (NRT use), outcome

(quitting), and confounders was all missing; thus, multiple imputation would not be appropriate

for my study. Furthermore, it is difficult to demonstrate if all missing data were missing at

random in the current study. In addition, missing information on the exposure variables,

outcomes, and potential confounders would need to be imputed, which would increase the

required data analysis and interpretation heavily. Because of these reasons, the multiple

imputation method for handling missing data was not conducted in the current study. Analysis

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was conducted among those with complete information. However, a comparison between those

who dropped out of the study and those who stayed in the study was conducted to determine if

dropouts were different from those who stayed in. I found no difference between the two groups

with regard to socio-demographic characteristics, nicotine dependence, and NRT use.

In the current study, analyses were conducted among those who were current smokers at baseline

and made at least one serious quit attempt at follow-up, and were re-interviewed at the end of 18

months of follow-up, These analyses included smokers who might lose to one or two follow-ups,

thus they did not have equivalent opportunities to provide complete data with regard to their

NRT use, serious quit attempts, and other covariates as those who did not lose to any follow-up.

Analyses among these smokers with missing data at follow-up one or two due to lost to follow-

up might introduce some bias. To reduce the potential bias due to missing data in the current

study in this way, I conducted complete case analyses (information available for baseline and all

three follow-ups). Findings from complete case analyses showed very similar results to those in

the current study (Appendix 12). This suggests the robustness of findings in my current study.

Research has indicated that if data are missing completely at random (MCAR), complete case

analysis (assuming MCAR) and multiple imputations (assuming missing at random, MAR) will

yield similar results with sizes of most coefficients and standard errors (differing by <3.4%); but

results based on missing not at random (e.g., Heckman selection model) will produce biased

results (up to 730% bigger).275 The missing mechanism may be determined by using extra

information gathered during the data collection exercise.275 Future studies may consider

collecting extra information during data collection about the cause of missingness.

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9.5.8 Level of Nonresponse

The overall response rate for smokers at baseline was 63%,276 which is similar to that in the

recent Canadian Tobacco Use Monitoring Surveys (overall response rate for Ontario: 61.3%,

67.5%, 61.3% and 61.6% for 2005, 2006, 2007 and 2008, respectively). Although there is no

necessary relationship between low response rates and bias,238, 277 higher response rates reduce

the potential for bias, and high response rates are usually viewed by investigators, journal editors,

and readers as a proxy for the representativeness of the sample.278 However, Biener and

colleagues compared demographic characteristics of respondents to tobacco surveys in

Massachusetts and California to population data in the early 1990s, when response rates were

high, and in more recent years, when response rates were lower, and found no evidence that

declining response rates have resulted in less accurate or biased estimates of smoking

behaviour.279

9.5.9 Representativeness of the OTS Sample

The response rate of this study was 63% for smokers at baseline, and was similar to that in the

recent surveys of CTUMS for Ontario. If nonresponders are similar to responders in every way,

the response rate does not affect generalizability to the surveyed population. However,

comparison between responders and nonresponders is challenging and difficult to conduct. One

way to assess this is to use the “continuum of resistance model”, in that late respondents can be

used as a proxy for non-respondents in estimating non-response bias.280 However, a few

studies280-282 have found that late responders do not differ significantly from earlier responders.

Although one study283 did find that its findings were consistent with the “continuum of resistance

model”, the bias resulting from nonresponse was arguably too small to be of concern with

respect to estimating alcohol consumption levels, the incidence of alcohol-related problems, and

the prevalence of hazardous drinking.

The focus of this study was to estimate the association between NRT use duration and smoking

cessation, rather than to estimate the prevalence of NRT use or cessation. Thus, the scientific

goal of this study was to assess the abstract universal hypothesis. Selecting representative

populations in the statistical sense will generally not enhance the ability to provide universal

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statements from observations, but selection of study groups for characteristics that enable a study

to distinguish effectively between competing scientific hypotheses will do so.227

Given this evidence, in this study, I did not apply the “continuum of resistance model” to

examine the potential non-response bias. Nonetheless, the representativeness of sample should be

reported by comparing the characteristics of smokers (e.g., age, sex, education level, cigarettes

smoked per day, and heaviness of smoking index) of smokers in this study to other population-

based surveys (e.g., CCHS) in a similar year, so that readers are aware of the smokers’ profiles in

this study. The representativeness of smokers in the OTS data to the smoker population of

Ontario in the CCHS 2007 data was assessed (see Appendix 11). Smokers were defined as those

who had smoked 100+ cigarettes in their lifetime and smoked at the time of survey or past 30

days.

Overall, there were more female and middle-aged people in the OTS than in the CCHS. There

were more people with high level of education (post-secondary graduation) in the CCHS than in

the OTS. The daily smoking was similar in the OTS and CCHS, but there were more heavy

smokers in the OTS than in the CCHS (details can be found in Appendix 11). It appears that the

OTS sample may not be a perfect representative sample of the smoking population compared to

the CCHS 2007 smoking population. Partially, this might be because the sample of OTS was

from several years (from 2005 to 2008), but the sample of CCHS was only from one year in

2007. As indicated by Lohr and Liu,284 sampling weights are crucial for estimating overall rates,

weights do not have as much of an effect on methodological models, and the basic conclusions

drawn from the models are the same with or without weights. Therefore, un-weighted analysis

was conducted in my current study. Furthermore, as I mentioned above, the scientific goal of this

study was to assess the association between NRT use duration and smoking cessation, which

should move from time- and place-specific observations to an abstract “universal” hypothesis,

such as “NRT increases smoking cessation”. When weights make a difference in the analysis,

they more often affect estimates of population means rather than estimates of association.285

Nonetheless, readers should be aware of the characteristics of smokers in this study.

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9.5.10 Confounding Effects

The major confounding variables included baseline variables of sex, daily smoking, cigarettes

per day smoked, intention to quit, self-perceived addiction, self-perceived easiness of quitting,

self-perceived benefit from quitting, ever use of NRT, bupropion or varenicline, ever use of other

quit methods, and home smoking restrictions, and follow-up variables of number of quit

attempts, use of other tobacco products, use of behavioral support, and use of other quit methods

(and other forms of NRT products without patches or gum for the association between patch use

or gum use duration and smoking cessation). The effects of these confounders were in line with

expectation. For instance, daily smoking was associated with a lower likelihood of quitting than

non-daily smoking; those who smoked more cigarettes per day were less likely to quit than those

who smoked fewer cigarettes per day; self-perceived addiction was associated with a lower

likelihood of quitting; those with home smoking restrictions were more likely to quit than those

without home smoking restrictions. In the current study, I considered much more potential

confounding variables than previous population-based studies. Confounders adjusted for in

previous population-based studies included tobacco dependence only (e.g., West et al. 67),

demographics and cigarette consumption (e.g., Pierce and Gilpin,63 Alberg,61 and Zhu et al.64),

demographics only without tobacco dependence (e.g., Buck and Morgan,60 and Ferguson et

al.62), or the study did not control for demographics or tobacco dependence confounding factors

(e.g., Reed et al.,286). In Alpert’s study,68 authors indicate that “Covariates included length of

abstinence reported at the beginning of the 2-year period (<6 months or between 6 months and 2

years) and nicotine dependence in the year before quitting with a high level of dependence

defined as smoking within 30 min of waking up in the morning and consuming ≥20 cigarettes

per day. Nicotine dependence was also controlled in a separate analysis using ordinal variables

for both time of first cigarette after waking up and number of cigarettes smoked per day before

quitting.” However, for the main results about NRT and other factors associated with likelihood

of smoking relapse (Table 3 in Alpert’s study), it appeared that smokers were stratified by light

(<20 cigarettes per day) and heavy dependence (≥20 cigarettes per day); consumption of

cigarettes per day or HSI was not controlled for. Thus, residual confounding effects from tobacco

dependence might exist in Alpert’s study. The effect of NRT observed in my current study was

independent of behavioural support, which is of importance. Because several population studies

found no significant effect of NRT use, people have suspected that NRT may not work in the

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real-world settings due to lack of behavioural support. Findings in the current study showed that

NRT, especially patches, helped smokers quit smoking, independent of behavioural support.

Information on co-morbidities (e.g., depression and mental disorders) and genetic factors was not

available in the current study. If smokers with mental disorders were distributed differently

among NRT use groups and smoking cessation rates were different between those with and

without mental disorder, the observed associations in relation to NRT use duration might be

distorted. An Australia study287 compared use of NRT, motivation to quit smoking, the

proportion of quit attempts, and smoking cessation at six months post-discharge among

hospitalized individuals with and without mental health disorders and found that there were no

differences in NRT use, motivation to quit, and smoking cessation at six months. The only

difference was quit attempts (34 among those with mental health disorders vs. 13 among those

without mental health disorders). This may suggest that the co-morbidity of mental illness is less

likely to be a confounder in the current study. Genetic factors may affect smoking cessation. Ray

et al.288 found that choline acetyltransferase gene variation is associated with prospective

smoking cessation and nicotine dependence. In this study,288 the authors conducted a systems-

based genetic association analysis in a sample of 472 treatment-seeking smokers of European

ancestry after 8 weeks of transdermal nicotine therapy for smoking cessation. The primary

outcome was smoking cessation (biochemically confirmed) at the end of treatment. The study

found that single-nucleotide polymorphisms (SNPs) clustered in the choline acetyltransferase

(ChAT) gene were individually identified as nominally significant, and a 5-SNP haplotype

(block 6) in ChAT was found to be significantly associated with quitting success. Single SNPs in

ChAT haplotype block 2 were also associated with pre-treatment levels of nicotine dependence

in this cohort. Genetic variation may also influence the effect of NRT on smoking cessation.

Lerman et al.289 found that genetic variation in nicotine metabolism is associated with the

efficacy of transdermal nicotine therapy. In this placebo-controlled trial,289 471 Caucasian

smokers were assigned either to a standard therapy (receiving 8-week transdermal nicotine

therapy; n=243) or to an extended therapy (receiving 6-month transdermal nicotine therapy;

n=228). The study found that extended therapy was superior to standard therapy in genotypic or

phenotypic reduced metabolizers (RMs) of nicotine (quit at 24 weeks: OR=4.78, 95% CI 1.74-

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13.13 among reduced genotypic metabolizers and OR=2.54, 95% CI 1.15-5.60 among reduced

phenotypic reduced metabolizers) but not in normal metabolizers (NMs) (quit at 24 weeks:

OR=1.47, 95% CI 0.90-2.41 for normal genotypic metabolizers and OR=1.60, 95% CI 0.95-2.71

among normal phenotypic metabolizers). Many genetic factors may be associated with smoking

cessation. The current study is not able to assess the potential confounding and modifying effects

of co-morbidities and genetic factors, which may be a limitation of the current study.

In the current study, it was found that those using any NRT or patches <4 weeks or using gum <8

weeks were less likely to quit smoking short- or long-term compared to not using these quit aids.

This perhaps was due to some residual confounding effects in tobacco dependence or other

confounding factors not included in the current study (e.g., genetic factors and co-morbidity).

In this study, confounders were identified using three criteria recommended in epidemiological

studies:227, 290 (1) the variable needs to be associated with the exposure; (2) the variable needs to

be associated with the outcome; and (3) the variable should not be an intermediate variable in the

causal pathway between exposure and outcome. If one incorrectly adjusts for a variable that is

not a confounder, overadjustment may happen. In general, overadjustment means control for a

variable that increases rather than decrease net bias or affects precision without affecting bias.291

Overadjustment bias generally happens when an intermediate factor or the proxy of the

intermediate variable is controlled for.291 In my study self-perceived confidence of quitting, self-

perceived addiction, and self-perceived easiness of quitting were all baseline variables. They

were not on the causal pathway from using NRT to quitting smoking, thus controlling for these

variables should not cause overadjustment bias. However, these variables might produce

unnecessary adjustment. Unnecessary adjustment occurs in four conditions: 1) adjusting for a

variable completely outside the system of interest; 2) adjusting for a variable that causes the

exposure only; 3) adjusting for a variable whose only causal association with variables of interest

is as a descendent of the exposure and not in the causal pathway; and 4) adjusting for a variable

whose only causal association with variables of interest is as a cause of the outcome.291

Controlling for unnecessary adjustment variables does not change the causal effect of exposure

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on outcome, but may change precision (gain or loss).291 These variables for self-perceived

addiction, confidence in quitting, and easiness of quitting were found to be associated with both

the exposure variables (any NRT, patch, or gum use) and the quitting outcomes, and were not on

the causal pathway (all baseline variables). They should reflect smokers’ addiction and ability of

quitting, and should be treated as tobacco dependence variables (such as HSI). As a test, I

conducted analysis for the association between using patches ≥8 weeks and quitting outcomes

without controlling for these variables and found similar but slightly smaller likelihoods of

quitting (RR=1.62, 95% 1.12-2.37 for short-term abstinence, and 2.40, 95% CI 1.04-5.53 for

long-term abstinence at the end of 18 months of follow-up), compared to not using patches. This

suggests that there were higher proportions of smokers who were more addicted to smoking, who

were less confident in quitting, and who perceived quitting as more difficult among those using

patches ≥8 weeks than among those not using patches. Without controlling for these variables,

the association between using patches ≥8 weeks and quitting outcomes would be slightly

attenuated. I believe that these variables should be controlled for and they did not produce

overadjustment bias.

9.5.11 Modifying Effects

In this study, a comprehensive list of potential modifying variables was assessed. No modifying

factors were found for the short- and long-term quitting outcomes. This might be because only a

small proportion of smokers used NRT for the recommended duration. A large sample might be

needed to detect modifying effects for the association between NRT use duration and categorical

smoking cessation outcomes.

No modifying effect for NRT use and behavioural support was found, due to small sample size

for combination use of NRT and behavioural support.

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9.5.12 Strengths of the Current Study

The strengths of the current study included using a representative sample of Ontario smokers, the

relatively large sample size (n=1,590), low rate of loss to follow-up (up to 17% for different

quitting outcomes), population-based longitudinal study in design, ability to control for many

covariates, using a long-term outcome (≥12 months of continuous abstinence), and information

on duration of NRT use.

Using the representative sample of smokers in Ontario, the findings of the current study were

more generalizable to the whole population of smokers than other studies using convenience

samples. Because of the large sample size, this study was able to detect significant differences in

different quitting outcomes, including short- and long-term quitting outcomes. However, due to

small sample for those who used inhaler or lozenge, this study was not able to estimate the

effects of these quit aids individually. Even for nicotine gum, this study was not able to detect a

significant effect on quitting outcomes, due to perhaps the combination of low effect in cessation

and small sample size.

Loss to follow-up may distort findings in longitudinal studies. A cut-off of 80% of follow-up rate

has been considered as a high quality of evidence in evidence-based medicine.292 The overall loss

to follow-up in the current study was relatively low (up to 17%). The comparison between those

who were included in the analysis and those who were lost to follow-up also showed that they

were almost the same in all aspects, except for two variables: age and quit attempts in the 12

months prior to baseline. Those who were lost to follow-up were younger and more likely (44%)

to make a quit attempt in the 12 months prior to baseline than those who were included in the

analysis (36%). In addition, for the quitting outcomes during any period of follow-up, everyone

was included in the analysis, which meant that no loss to follow-up occurred for the analysis of

quitting outcomes at any follow-up. Thus, loss to follow-up would not influence the study results

substantially and the quality of evidence from this study should be high.

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The longitudinal study design helped to establish a causal relationship between NRT use and

smoking cessation. This study design is much stronger than cross-sectional study design in

causal relationship establishment. As mentioned above, the current study was able to control for

a comprehensive list of covariates, which made the findings of the current study much more

robust than some previous studies controlling for only a few covariates or none.

Using a long-term outcome, the current study might be able to provide reasonable estimates of

maintenance or relapse for different types of NRT products.53 Nicotine patches were found to be

more effective than any NRT or gum to sustain long-term cessation, which might be of

importance. This finding has not been reported in previous population-based studies. This might

suggest that nicotine patches should be encouraged for assisting smokers to quit in the general

population.

The majority of previous population-based studies have not examined the effects of NRT on

smoking cessation in relation to its duration of use. Only one population-based study68 reported

that using NRT >6 weeks had no significant effect on relapse. The current study had information

on duration of NRT use and by type of NRT use (any NRT, patches, and gum), which was also

an important strength of the current study.

9.5.13 Limitations of the Current Study

A potential source of bias is reliance of self-reported NRT use and quit rates. However, the

reliability of NRT use and smoking status was determined by two relevant questions and a high

Kappa value (0.99) was obtained for both NRT use and smoking status, which meant that these

two measures had high reliability. The reliability on quit duration and NRT use duration could

not be determined in the current study. A review264 by the SRNT Subcommittee on Biochemical

Verification concluded that biochemical validation is not always necessary in smoking cessation

studies, because the levels of misrepresentation were generally low (0% - 8.8%), based on four

major papers.293-296 The SRNT review264 also concluded that there is little reason to expect

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differential misrepresentation rates between biochemical validation and self-reported smoking

status in most smoking cessation studies. A recent Canadian study265 using representative data

for Canadian population also showed no significant difference between national estimates of

smoking prevalence based on self-report versus urinary cotinine concentration (smoking

prevalence based on self-report was 0.3 percentage points lower than urinary cotinine

concentration). Nevertheless, future studies may consider using biomarkers to confirm smoking

status and a diary to confirm duration of quitting and NRT use.

Another limitation is no information on doses of gum and patch use in the current study. The

2009 Cochrane review54 found that there was a significant benefit of 4 mg gum compared with 2

mg gum, but weaker evidence of a benefit from higher doses of patches in highly dependent

smokers. Future studies may consider collecting information on dose of NRT use.

Loss to follow-up may be another potential bias in this study, as in all longitudinal or cohort

studies. However, it was found that those lost to follow-up did not differ from those who were

followed- up on all aspects in relation to smoking at baseline. In addition, the proportion of loss

to follow-up in this study was low (<17%), so this would not have much impact on the findings

of the current study.

Because of the small proportion of smokers using both NRT and behavioural support, this study

was unable to determine the potential modifying effect of behavioural support on the association

between NRT use duration and quitting outcomes. A recent study297 showed that combination

NRT was more successful than single NRT (OR 1.42, 95% CI 1.06-1.91), while single NRT was

associated with higher success rates than no medications (OR 1.75, 95% CI 1.34 to 2.22).

Because of the small proportion of concurrent use of two or more forms of NRT, the current

study could not assess the effect of combination use of NRT products. In addition, information of

NRT use duration was only available for the first three follow-ups, so that long-term abstinence

(e.g., >=2 years) could not be examined by NRT use duration. Certain confounding variables

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were not able to be controlled in the current study, such as co-morbidities and genetic factors.

Future studies may need to consider these factors.

Another limitation is small sample size in subgroups, especially for long-term abstinence (n=1

for using gum ≥8 weeks and n=4 for using gum <8 weeks). For these groups, even slight

misclassification or selection bias could drastically affect the results. The presence of small

counts may cause large statistical biases affecting the point estimates, even without

epidemiologic biases.298 Many methods have been recommended to correct the small sample size

problems, including exact logistic regression,299 and Firth’s penalized likelihood method.300

Exact logistic regression refers to exact conditional inference for binomial data that are modelled

by a logistic regression, and exact inference is reliable no matter how small or imbalanced the

data set is.301 Simulation studies have shown that Firth-adjusted results are comparable with

exact conditional analysis for small sample size data even with a zero cell.302, 303

To correct the small sample size problems in my study, I conducted exact logistic regression and

Firth’s logistic regression. Unfortunately, exact logistic regression had an insufficient memory

issue with SAS so that results could not be estimated even after increasing memory for SAS use.

Results from Firth’s logistic regression showed similar findings to those using Poisson regression

with robust variance estimation for long-term abstinence at the end of 18 months of follow-up

(for gum use, results from Firth’s logistic regression: OR=0.36, 95% CI 0.12-0.86, p=0.037 for

using gum <8 weeks and OR=0.68, 95% CI 0.08-2.68, p=0.65 for using gum ≥8 weeks; results

from the Poisson regression: RR=0.34, 95% CI 0.12-0.92 for using gum <8 weeks and RR=0.56,

95% CI 0.08-3.78 for using gum ≥8 weeks, compared to not using gum; for patch use, results

from Firth’s logistic regression: OR=0.50, 95% CI 0.21-1.09, p=0.091 for using patches <8

weeks and OR=2.56, 95% CI 1.00-5.87, p=0.033 for using patches ≥8 weeks; results from the

Poisson regression: RR=0.57, 95% CI 0.26-1.26, p=0.17 for using patches <8 weeks and

RR=2.62, 95% CI 1.25-5.50, p=0.011 for using patches ≥8 weeks). Although Firth’s logistic

regression confirmed my findings from Poisson regression with robust variance estimation, how

much small sample problems were reduced by this method was not clear. Therefore, readers

150

should be aware that these estimates were based on a very small sample size and the estimates

would be changed dramatically with even a slight misclassification bias on the outcome. Future

studies with a larger sample size for the long-term outcome by using gum or patches ≥8 weeks

are needed.

9.6 Implications of the Current Study

Using NRT, especially patches, for the recommended duration of eight or more weeks of

treatment in the general population of smokers increase the likelihood of short-term and long-

term abstinence. However, because only a small proportion of smokers used NRT for the

recommended duration, more efforts are needed to encourage smokers using nicotine patches for

the recommended duration. Smokers expressed that cost of stop-smoking medications was an

obstacle for them to use NRT long enough (Appendix 9).304 Lowering the cost either by

subsidizing or providing free NRT should help smokers use NRT appropriately, and thus may

increase quit rates at the population level. Efforts are also needed to improve the understanding

that cost of stop-smoking medications is much cheaper than cigarette smoking in the long run.

Needless to say, the health benefits from quitting smoking are substantial.

Findings of the current study also indicate that using NRT for suboptimal duration (<8 weeks)

was not associated with smoking cessation compared to not using NRT. Advertisements about

NRT products should emphasize how long a smoker needs to use it, rather than just how easy it

is to use and how useful it is. Smokers should be better informed that using NRT less than the

recommended duration is not effective on smoking cessation and that it is very important to use

NRT for the recommended duration.

Longer duration of NRT use may be needed for some smokers. The OTC NRT label advises

users to stop using nicotine gum at the end of 12 weeks and stop using nicotine patches at the end

of 10 weeks.47 However, when nicotine gum was available by prescription only, patients were

instructed to use the medications for six months.47 The shorter treatment duration for OTC NRT

was probably due to concerns about the abuse and dependence potential.47 Studies have shown

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that short-term (6-12 weeks)305 and long term (4-6 months)306 use of NRT is safe. Long-term use

(4-6 months) of NRT was unrelated to any cardiovascular illnesses or other serious side effects

among the 3,094 participants in the Lung Health Study.306 A recent review study307 reports that

the use of NRT is associated with a variety of side effects among clinical trial participants.

However, the majority of these side effects are minor, including increased risk of nausea and

vomiting, gastrointestinal complaints, insomnia, mouth and throat soreness, and skin irritations,

although heart palpitations, chest pains, and mouth ulcers were also reported. Any potential risk

with long term NRT use appears to be negligible compared to the risk of continuing smoking.

Shiffman et al.308 estimated the incidence of persistent use of OTC nicotine gum and patches

using household purchase data. They found that the percentage of households that purchased

NRT products ≥6 months was 2.3% for nicotine gum (among 805 households) and 0.9% for

nicotine patches (among 2050 households). The study308 concludes that persistent use of nicotine

gum and patches is very rare and has not increased with the transition to OTC use. A recent

simulation study309 compares potential population-wide benefits and risks, by examining the

potential impact of increased NRT use for smoking cessation on future US mortality. The

study309 found that even after assuming some harm from long-term NRT use, the benefits from

increased cessation success far outweigh the risks. In the current study, longer use of NRT

products was generally low. The proportion of smokers using NRT products ≥20 weeks was

1.7%, 0.4%, and 1.0% among those who made a serious quit attempt, and 4.0%, 1.4%, and 4.6%

among NRT users, patch users, and gum users, respectively. However, the persistent use of NRT

is an under-investigated issue.310 Currently the safety of persistent use of NRT is lacking. Large-

scale studies with the primary aim of monitoring for misuse of OTC NRT and assessing the

possible physical and mental health risks of persistent NRT use is needed.310

The current study showed that smokers using patches ≥8 weeks were 2.6 times more likely to

quit long-term than not using patches, but using gum ≥8 weeks was not associated with a higher

likelihood of long-term quitting than not using gum. This might suggest that nicotine patches

rather than gum should be promoted to smokers who are attempting to quit in the general

population. In addition, studies have shown that combination use of NRT products is more

effective than single use of NRT.47 Also combination of NRT and other pharmacotherapy (e.g.,

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bupropion SR and varenicline) may be necessary, as well as in combination with behavioural

support. Perhaps, smokers may start with a single form of NRT, as it is easy to access and

available OTC. If it does not work, combination with other forms of NRT should be used. Then,

combination with bupropion or varenicline should be applied. Behavioural support can be used at

any stage. Actually, Zapawa et al.47 have recommended that combination NRT therapy should be

considered for all smokers, especially those who are unable to quit smoking using a single form

of NRT after reviewing the current literature.

In a separate analysis, I found that cost of NRT was a barrier for smokers using NRT for eight or

more weeks. Many jurisdictions (such as Minnesota,311 Ohio,312 New York,253 Ontario,251 and

England250) have free NRT programs. However, little is known about how much free NRT

should be provided. A recent quasi-experimental study by Cummings et al.253 indicated that the

quit rate at 12 months for the 4-week supply group did not differ significantly from the 6-week or

8-week groups, although the actual use duration was significantly associated with quit rate (the

longer the use the higher the quit rate). Many smokers received more free NRT but left NRT

unused in Cummings et al.’s study.253 This study raised an important question about free NRT

programs: how much free NRT should be provided? Perhaps subsidized NRT could be a choice,

as smokers would need to pay some share for the cost of NRT, which might encourage smokers

to finish all NRT products they purchase. More studies are needed to answer this question.

Although NRT is a first-line recommendation for treating tobacco dependence, having been

shown to increase cessation rates by 1.5 to 2 times across a wide range of populations and

settings,47 other tobacco control strategies should not be neglected. Tobacco taxation, restrictions

on smoking in public and work places, adequately funded mass media campaigns, bans on

advertising, and health warnings on packages have been shown to be very effective in reducing

smoking in the general population.313 Comprehensive tobacco control strategies including these

evidence-based policies are necessary, and using NRT products should be a part of the

comprehensive strategies.

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9.7 Suggestions for Further Studies

1. Comparison between different doses of NRT in the general population of smokers

2. Use of combinations of different forms of NRT in the general population of smokers

3. Use of combinations of different forms of NRT with behavioural support in the general

population of smokers

4. Use of combinations of different forms of NRT with other stop-smoking medications (e.g.,

bupropion SR and varenicline)

5. Comparisons of different forms of NRT with other types of products (e.g., e-cigarettes) in the

general population of smokers

6. Comparisons of different duration of NRT use (e.g., 8-12 weeks vs. >12 weeks, or 8-20 weeks

vs. >20 weeks)

7. Cost effectiveness analysis of free NRT programs (how long or how many free NRT products

should be provided)

8. Comparison between free NRT programs and subsidized programs to examine which

programs are more effective in smoking cessation in the general population.

9. Use a diary approach to assess the association between NRT (patch and gum) use duration

and smoking cessation

10. To investigate the association between NRT use duration and long-term quitting outcome

(e.g., 5-10 years of follow-up)

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Chapter 10: Conclusions

Findings from this population-based representative sample of smokers suggest that both type and

duration of NRT quit aids play important roles in smoking cessation. Using nicotine patches for

the recommended duration (≥8 weeks) is associated with successful short- and long-term

abstinence among smokers, demonstrating the generalizability of clinical trials of NRT use to the

general population of smokers. This suggests that smokers who choose to use NRT to quit

smoking should be encouraged to use nicotine patches for at least eight weeks.

Previous studies have observed that quitting rates are higher for smokers who use NRT for a

longer duration. 238, 266, 314 People may argue that reverse causation cannot be ruled out for the

association between NRT use duration and quitting outcomes.253 However, as indicated in my

discussion, this reverse causation could not explain what was found in this study: using patches

≥8 weeks but not using gum ≥8 weeks was associated with higher quit rates, compared to their

counterparts; and using gum <8 weeks was associated with a lower likelihood of quitting than

not using gum. A recent randomized clinical trial also found that longer use duration (24 weeks

of nicotine patches) was associated with a higher quit rate than shorter use duration (8 weeks of

nicotine patches plus 16 weeks of placebo). These suggest that use duration of NRT quit aids

does play an important role in smoking cessation.

In this study, I found that the short-term abstinence rate was much higher during any period of

follow-up than at the end of 18 months of follow-up. For example, the short-term quit rate was

81.5% during any period of follow-up but 34.4% at the end of 18 months of follow-up for using

patches ≥8 weeks. Because using patches ≥8 weeks was associated with higher quit rates for both

short- and long-term abstinence compared not using patches, and the RR for long-term

abstinence was higher than that for short-term abstinence, this suggests that some smokers

relapsed during follow-up but recovered from relapse at the end of follow-up again. A few

studies have demonstrated that nicotine patches can help recover from relapse. Ferguson et al.266

compared recovery rate from a lapse among 509 subjects (240 active and 269 placebo) who

155

lapsed during weeks 3-5 of treatment in a randomized, double-blind placebo-controlled trial of

21-mg nicotine patches, and found that active patch use increased the likelihood of recovery

from a lapse both at 6 weeks (8.3% vs. 0.8%, RR=11.0, p<0.001) and at 10 weeks (9.6% vs.

2.6%, RR=3.7, p<0.001) compared to placebo. The study by Schnoll et al.238 also reported that

using patches for 24 weeks reduced the risk for smoking lapses and increased the likelihood of

recovery to abstinence after a lapse compared with 8 weeks of nicotine patches. These findings

indicate that smokers should be encouraged to continue using nicotine patches even if they lapse

or relapse to smoking. Smokers should be better informed that it is important to continue using

nicotine patches after relapse to smoking, because nicotine patches can help smokers who relapse

to resume cessation.

In this study, I also found that using nicotine gum <8 weeks was associated with a lower

likelihood of long-term abstinence. This might be due to residual confounding effects. Although

many covariates were controlled for in this study, tobacco dependence variables (including daily

smoking status, number of cigarettes smoked per day, heaviness of smoking index, and self-

perceived addiction) controlled for in adjusted analyses might not fully capture the difference in

real tobacco dependence (such as genetic difference in tobacco dependence) between those who

used nicotine gum <8 weeks and those who did not use gum. In addition, co-morbidity and

genetic variables were not collected in this study, which could also introduce confounders for the

relationship between NRT use duration and smoking cessation. Smokers should be better

informed of the importance of using NRT long enough to reach their desired goal – smoking

cessation.

In this study it was found that using patches ≥8 weeks increased the likelihood of quitting but

using gum ≥8 weeks did not increase the likelihood of quitting, compared to their counterparts.

What factors might account for this difference, the medication or the difference between gum

and patch users? After comparing the characteristics between smokers using gum only and using

patches only (without using other NRT products), it was found that the two groups were very

similar. The major differences between the two groups were education (a higher proportion of

post-secondary graduation in the group using gum only), self-perceived addiction (a lower

156

proportion in the group using gum only), home smoking restrictions (a higher proportion in the

group using gum only), beliefs about quit medication (a lower proportion of smokers believing

medications making quit easier in the group using gum only), and using other tobacco products

(e.g., cigars and snus) at follow-up (a higher proportion in the group using gum only). When

comparing those using gum ≥8 weeks only to those using patches ≥8 weeks only (without using

other NRT products), the only difference was an environmental factor (someone making quitting

more difficult: a higher proportion in the group using patches ≥8 weeks only) (comparisons can

be found in Appendix 13). These differences seemed in favour of the group using gum only in

relation to smoking cessation (higher education, less self-perceived addiction, and higher

proportion of home smoking restrictions in the group using gum only). These findings suggest

that the different impacts of using gum ≥8 weeks and using patches ≥8 weeks was more likely

due to the medication per se (patches: easy to use, providing stable nicotine supply, and

relatively high dose of nicotine in each piece), rather than the difference in demographic and

tobacco dependence characteristics of users. However, because gum users were less likely to

believe that quit medications could help them to quit and more likely to use other tobacco

products, it would be important to better educate smokers that quit medications are helpful in

assisting quitting and using other tobacco products should be discouraged among those who want

to quit smoking.

Cost of NRT was a barrier for smokers using NRT for eight or more weeks in my study. Many

jurisdictions provide free NRT to smokers who want to quit. However, little is known about how

much free NRT should be provided. A recent quasi-experimental study by Cummings et al.253

has indicated that providing more free NRT does not automatically transfer to higher quit rates.

Future studies are needed to answer the questions: how much free NRT should be provided?

Would subsidized NRT be a better choice than free NRT?

In my sensitivity analysis, it was found that using nicotine patches ≥8 weeks increased the short-

term quit rate among those who were not motivated to quit immediately and those who tried

serious quit attempts. The two groups were very similar in socio-demographic characteristics and

smoked same cigarettes per day (10 cigarettes/day), but smokers in the sensitivity analysis had

157

slightly higher proportions of daily smoking and high level of HSI, compared to those in the

analysis for those who made a serious quit attempt (81% vs. 77% for daily smoking and 18% vs.

11% for high level of HSI). This suggests that nicotine patches should be encouraged to be used

among all smokers, even among those who are not ready or unmotivated to quit smoking.

However, no cases of long-term abstinence were from those who were not motivated to quit

smoking. More studies are needed to investigate whether an even longer duration (e.g., six-

months or 12-months) of nicotine patches or other NRT products is necessary to achieve long-

term abstinence for those who are not motivated or unable to quit smoking. Clinical trials244, 246

have shown that using NRT 6-12 months increase long-term abstinence rate at 12- and 24

months compared to placebo among smokers who are not motivated or unable to quit smoking.

Because the majority of smokers did not use NRT quit aids for the recommended duration of

treatment (≥8 weeks), more effort is needed to promote the use of NRT products, especially

nicotine patches for the recommended duration among smokers making quit attempts. The

responsibility should not rest on smokers only. All channels should be used to promote using

NRT products for long enough periods. Telephone quit lines, web based programs,

pharmaceutical industries (their instructions about how to use these medications and their

websites about these products), and health care practitioners (e.g., physicians, pharmacists,

dentists, and nurse practitioners) all should be utilized to promote the use of NRT products,

especially nicotine patches for eight or more weeks.

Although findings of my study showed that using nicotine patches for eight or more weeks

helped smokers quit smoking, NRT is not a panacea. Comprehensive tobacco control strategies

including evidence-based policies313 (e.g., tobacco taxation, smoke-free laws, adequately funded

mass media campaigns, bans on advertising, and health warnings on packages) are necessary to

reduce smoking-related health problems at the population level. Using NRT products should be a

part of these comprehensive strategies.

158

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Appendix 1. Summary of Population-Based Studies

Table 37. Summary of population-based studies assessing NRT effectiveness in quitting smoking

Authors Year of publication

Design Respondents, sample size and eligibility criteria

NRT measures

Outcome measures

Analysis Results Potential issues

Zhu, et al. 200064

Cross-sectional survey

Representative random sample of California adults population (aged 18+) (1996 California Tobacco Survey), smokers 12 months prior to the survey, made at least one intentional quit attempt lasted at least 24 hours (n=4,480)

NRT use for the last quit attempt

Quit rate (former smokers at the time of survey)

Weighted percentage of quit rate and chi-square test for quit rate

Quit rate was 30.3% for NRT, 23.7% for NRT plus counselling and 16.3% for non-assistance

No adjusted analysis conducted for NRT and non-assistance group comparison; no information on long-term quit between NRT and non-assistance groups

Buck, et al.

200160


Representative general adult population of England 1995; n= 2,246 smokers who made cessation attempts; aged 16-74, smoked one or more cigarettes daily

Ever use NRT (gum and patches)

Ex-regular smokers versus current smokers

Probit analysis; controlled for social class, education, gender, age, ethnicity, area, marital and health status

Users of nicotine gum and patches were less likely to have given up smoking than non-users (p<0.01); no information on quit rates by NRT use

Recall bias for NRT ever use among long time quitters (might not be able to recall NRT use); In the analysis for recent quitters, ever use of NRT might not be relevant

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Pierce, et at. 200263


Representative general adult population of California (Tobacco Surveys of 1992, n=5247, 1996, n=9725 and 1999, n=6412)

NRT use for their most recent quit attempt in the last year

Rates of cessation attempts ( 1 in the last year and cessation duration for recent former smokers

Cox model to examine the effect of pharmaceutical aid use on duration of abstinence, adjusting for age, sex, race, education and cigarette consumption a year earlier

NRT use was associated with an increased quit rate for each year, but the effect in 1999 (over the counter NRT was available) was only short-term (until 3 months); no formation on quit rates by NRT use

Recall bias for long time quitters about NRT use; behavioural support and previous quit attempts were not controlled for; suboptimal duration of NRT use (median 14 days)

Alberg et al. 200561

Cohort study

Cohort members (n=1954) who were current smokers in 1989 and provided data on NRT use and smoking status in 1998

Ever use NRT (gum and patches)

Smoking cessation

Multiple linear regression analysis on the difference in the percentage who quit smoking in NRT users minus NRT non-users was estimated, adjusted for socio-demographics and amount smoked

30% of NRT users and 39% of nonuser quit smoking (p<0.05)

Recall bias for NRT ever use among long time quitters; no information on behavioural support; cohort members were not a representative of the general population

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Ferguson, et al. 200562

Cohort study

Cohort members (n=2,069) who received smoking treatment service, aged 16+

NRT use in combina-tion with beha-vioural support

Prolonged abstinence at 52 weeks from original quit date(self-reported, or CO validated)

Logistic regression controlled for age, gender, ethnicity, social status, tobacco dependence, type of referral, and area of service

Quit at 52 weeks (CO validated) was 15.2% in NRT only group, 7.4% in NRT plus bupropion, and 25.5% in non-pharmacological group

Potential confounding effect of behavioural support was not controlled; this is a non-representative sample of the general population.

Miller, et al. 200566

Cohort study

Eligible smokers of the New York State Smokers’ Quitline (n=1,464)

6-week course of nicotine patches

7-day point prevalence of quitting at 6 month

Logistic regression analysis, adjusted for social-demographics and smoking amount

Quit rate was 33% for NRT recipients, and 6% for those who were eligible but did not receive NRT due to mailing error; OR = 8.8 (95% CI 4.4-17.8)

Only short-term quit (7-day); no adjustment for behavioural support; non-representative sample of the general population

Swartz, et al. 200565

Cohort study

Callers of Maine Tobacco HelpLine in Portland (n=535) who were eligible to receive free NRT

A continuous supply of NRT with no <15 days of disruption in drug supply

7-day, 30-day point prevalence and 6-month continuous abstinence, 6-month after assistance

Descriptive analysis

Among survey respondents, the quit rates of 7-day, 30-day and 6-month abstinence were 15.7%, 15.7% and 10.8% for self-help, 27.1%, 23.4% and 13.1% for counselling, and 39.1%, 35.7% and 19.7% for counselling plus NRT

NRT users received more behavioural support than non-NRT users; No adjusted analysis; non-representative sample of the general population;

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West, et al. 200767

Cohort study

Cohort study with data collection by the internet, smokers of ≥5 cigarettes/day, aged 35-65, intention to stop smoking within the next 3 months (n=492 smokers in phase I; n=732 smokers in phase II) who made a quit attempt without formal behavioural support or bupropion

NRT use during the past 3 months

Continuous quit for 6 months

Logistic regression analysis, adjusted for Fagerstrom test for nicotine dependence score

Calculated quit rates† were 3.9% and 10.2%, and 3.7% and 7.4% for not using NRT and NRT users in phase I and phase II, respectively; OR=3.0 (95% 1.2-7.5) in phase I, and 2.1 (95% 1.0-4.1) in phase II

No adjustment for previous quit attempts, and NRT use; non-representative sample of the general population

Alpert et al. 201268

Cohort study

From a probability sample of 6,739 Massachusetts adults; Analysis included 787 recent quitters (quit <2 years) in the first and second waves

Any NRT use and NRT use >6 weeks

Smoking relapse by second and third waves

Generalised linear latent and mixed models multilevel logistic modelling

Calculated relapse rates of not receiving NRT or counselling, received NRT only, and received NRT and counselling were 30%, 34% and 21% among prior heavy dependent smokers; and 22%, 45% and 38% among prior light dependent smokers, respectively; the relapse OR=1.28 (95% CI 0.52-3.16) for using NRT>6 weeks among prior heavy dependent smokers; and 3.29 (95% 0.57-18.9) among prior light dependent smokers, compared to not using NRT or professional help

Residual confounding effects from nicotine dependence might exist from stratified analysis (heavy vs. light dependence); The overall response rate was low (46%) and the follow-up rate was low too (56%); no examination of the effect of nicotine patches and gum separately;

† Quit rates were not provided by the study, but calculated based on the

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Appendix 2. Questions and Variables Used in Identification of Participants

Baseline smokers were asked the question “SB13_X” (X indicating follow-up, e.g., SB13_1 for

follow-up one and SB13_2 for follow-up two): “Compared to 6 months ago, that is since [last

interview time], would you say that you are now smoking …” (with responses: 01 – the same as

you were smoking; 02 – more than you were smoking OR; 03 – less than you were smoking; 04

– quit completely [DO NOT READ]; 06 – Don’t know; and 09 – Refused). Those who

responded “01 – the same …”, “02 – more than …”, “06 – Don’t know” and “09 – Refused” to

the question “SB13_X” were asked the question “SB14_X”: “At any time during the past 6

months, did you change your smoking behaviour with the intention of quitting or reducing the

amount you smoke?” (with responses: 01 – yes; 02 – No; 06 – Don’t know; and 09 – Refused).

Those who responded “03 - less than …” to the question “SB13_X” or “01 – Yes”, “06 – Don’t

know” or “09 – Refused” to the question “SB14_X” were then asked the question “SB15_X”:

“How did you change your smoking behaviour when you were trying to reduce the amount you

smoke in the past 6 months? Did you try to quit smoking completely?” (with responses “01 –

Yes; 02 – No; 06 – Don’t know; and 09 – Refused). Those who responded “Yes” to the question

“SB15_X” were asked the question “QB11a_X”: “How many times have you made a serious

attempt to quit smoking in the past 6 months? By serious, we mean that you made a conscious

attempt to stay off cigarettes for good.” Those who responded “04 – Quit completely” to the

question “SB13_X” were asked the question “QB11b_X”: “In the past 6 months, that is since

[last interview time], how many times did you make a serious attempt to quit before you were

able to quit smoking? By serious, we mean that you made a conscious attempt to stay off

cigarettes for good.” Those who made a serious attempt to quit based on the responses to the

questions “QB11a_X” and “QB11b_X” at any follow-up were the eligible respondents in the

current study.

The flow diagram for the questions to identify those who made a serious attempt to quit at

follow-up is shown below.

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Figure 5. Flow diagram for the questions in the OTS study to identify those who made a serious attempt to quit at follow-up

SB13_XCompared to 6 months ago, that is since [last interview time], would you say that you are now smoking … 01 – the same as you were smoking GOTO SB14_X 02 – more than you were smoking OR GOTO SB14_X 03 – less than you were smoking GOTO SB15_X 04 – Quit completely [DO NOT READ] GOTO QB11b_X 06 – Don’t know GOTO SB14_X 09 – Refused GOTO SB14_X

SB14_XAt any time during the past 6 months, did you change your smoking behaviours with the intention of quitting or reducing the amount you smoke? [DO NOT READ CATEGORIES] 01 – Yes GOTO SB15_X 02 – No GOTO DSB23_X 06 – Don’t know GOTO SB15_X 09 – Refused GOTO SB15_X

SB15_XHow did you change your smoking behaviour when you were trying to reduce the amount you smoke in the past 6 months?...” Did you try to quit smoking completely? [If necessary, remind respondent “during the past 6 months”] 01 – Yes GOTO QB11a_X 02 – No GOTO SB16_X 06 – Don’t know GOTO SB16_X 09 – Refused GOTO SB16_X

QB11a_XHow many times have you made a serious attempt to quit smoking IN THE PAST 6 MONTHS? By serious, we mean that you made a conscious attempt to stay off cigarettes for good. [DO NO READ CATEGORIES] 01 – ______ enter number (if range given, use midpoint) GOTO QB18a_x 06 – Don’t know GOTO SB16_X 09 – Refused GOTO SB16_X

QB11b_XIn the past 6 months, that is since [last interview time], how many times have you made a serious attempt to quit before you were able to quit smoking? By serious, we mean that you made a conscious attempt to stay off cigarettes for good. [DO NO READ CATEGORIES] 01 – ______ enter number (if range given, use midpoint) GOTO QB18b_x 06 – Don’t know GOTO SB24_X 09 – Refused GOTO SB24_X

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Appendix 3. Questions and Variables Used in Identification of Outcome Measures and NRT Use

Outcome Measures

These outcome measures will be determined using the variables “How long ago was it that you

last smoked a cigarette?”(“dvlastcig_x”, with the response categories “01 - one week or less”,

“02 – more than one week but less than one month”, “03 – 1 to 6 months ago”, “04 – 7 to 11

months ago”, “05 – 12 to 17 months ago”, “06 – 18 to 23 months ago” and “07 – 24 months or

more ago” ), and “In the past 6 months, what was the longest amount of time that you stayed

smoke-free?” (“SB21b_x”) and the days of abstinence were obtained from a derived variable

“SB21num_x” for the longest time of abstinence in days. For the outcome at final follow-up,

duration of abstinence will be determined by dvlastcig_x (the median value of this variable will

be used as the continuous outcome. For instance, the quit duration will be calculated as

[30+2.5*30 = 100 days] for those who quit between one month and 6 months.) For the outcome

of longest abstinence at any follow-up, duration of abstinence will be determined by SB21num_x

and dvlastcig_x, whichever had the largest value during any follow-up. For instance, if

SB21num_1 = 45 days and dvlastcig_1 = 1 (for one week or less, the median value is 3.5 days)

at follow-up one, SB21num_2 = 90 days and dvlastcig_2 = 4 [for 7 to 11 months ago, the median

value is 272.5 days (i.e., 365/2 + 3*30)] at follow-up two, and SB21num_3 = 80 days and

dvlastcig_3 = 2 [for more than one week but less than one month, the median value is 18 days

(i.e., (29+7)/2)] at follow-up three. Thus the longest abstinence from smoking at any follow-up

will be 272.5 days from dvlastcig_2.

Measures of NRT Use Duration

Duration of nicotine patch use were determined as follows: 1) response of “Yes” to the question

“In the past 6 months, did you use nicotine patches to help you quit smoking” (QA2aa), and 2)

answers to the question “Over the past 6 months, how long did you use the patch?” Duration of

other forms of NRT use (gum, inhaler and lozenges) will be determined in the same way. The

total duration of NRT use were calculated as the sum of the durations for nicotine patch, gum,

inhaler and lozenge use over the past six months. If respondents used these products at the same

time, one duration with the longest time was used (very few used two or more forms of NRT

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products at the same time). If respondents did not use any NRT, the duration for NRT use was

coded as zero.

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Appendix 4. Determination of Variables for Potential Confounding Factors and Effect Modifiers

Age (variable name ‘dvage_0’): age at baseline was treated as a continuous variable.

Sex (dvsex_0): male was the reference group.

Education at baseline (de2_0): the highest level of educational attainment at baseline or follow-

up (time-variant variable) was categorized as less than high school, high school, some post

secondary school, and university degree (reference group).

Marital status at baseline (de4_0): classified as married, widowed/divorced/separated and

single.

Self-perceived general health at baseline (dvhealth_0): self-perceived general health at

baseline was categorized as “good to excellent” (reference group), “poor to fair”.

Tobacco dependence at baseline (dvhsi3_0): heaviness of smoking index (HSI)315 was

determined based on two questions at baseline “How soon after waking do you smoke your fist

cigarette” (Within 5 minutes: 3 points; within 30 minutes: 2 points; within 1 hour: 1 point), and

“How many cigarettes do you smoke per day?” (More than 30 per day: 3 points; 21 to 30 per

day: 2 points; and 11 to 20 per day: 1 points). Three categories will be used in data analysis (HSI

0-2 points for low (reference group), HSI 3-4 points for moderate and HSI 5-6 points for high

dependence).

Average number of cigarettes per day smoked at baseline (sb7num_0 and sb8num_0): based

on the questions about average number of cigarettes smoked on weekdays and weekend days.

Using other tobacco products such as chewing tobacco snuff cigars or pipes at baseline and

follow-up (sb28_x) (yes vs. no): based on the responses to the question “Besides cigarettes in the

past 6 months, have you used any other tobacco products such as chewing tobacco, snuff, cigars

or pipes?”

Number of serious quit attempts in lifetime at baseline (qb10_0): based on the response to the

question “How many times have you EVER made a serious attempt to quit smoking? By serious,

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we mean that you made a conscious attempt to stay off cigarettes for good.” This variables was

treated as a continuous variable.

Made a serious quit attempt in the last 12 months at baseline (qb10a_0): based on the

responses of “<1 month ago”, “1-6 months ago”, “7-12 months ago” and “currently in a quit

attempt” to the question “When did your last serious quit attempt end?” Denominator includes

the response “more than 1 year ago”, apart from the above four responses”.

Intention to quit at baseline (qb7_0): based on the response to the question “Are you planning

to quit smoking within the next month, within the next 6 months, sometime in the future, beyond

6 months, or are you not planning to quit? Categorized as “within next month”, “within the next

6 months”, “sometime in the future”, beyond 6 months” and “Not applicable” vs. “not planning

to quit”.

Setting a firm quit date for the planning quit at baseline (qb9_0) (yes vs. no): based on the

response to the question “Have you set a firm quit date?”

Self-perceived addiction to smoking at baseline (ad1_0): based on the response to the question

“Thinking about your own smoking, would you say that you are not at all addicted to cigarettes,

somewhat addicted to cigarettes or very addicted to cigarettes?” categorized as “not at

all/somewhat addicted” (reference group) or “very addicted”.

Self-perceived easiness of quitting smoking at baseline (qb1_0): based on the response to the

question “How easy or hard would it be for you to completely quit smoking if you wanted to?”

categorized as “very easy/somewhat easy” (reference group) or “somewhat hard/very hard”.

Self-perceived confidence of quitting smoking at baseline (qb2_0): based on the response to

the question “How confident are you that you would succeed if you decided to quit

COMPLETELY in the next six months?” categorized as “not at all confident/not very confident”

or “fairly confident/very confident” (reference group).

Social support for quitting (qb3_x) at baseline and follow-up (yes vs. no): based on the

response to the question “If you decided to quit smoking, do you have at least one person you

could count on for support?”

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Someone making quitting difficult (qb4_0) at baseline (yes vs. no): based on the response to

the question “Is there anyone who might make it more difficult for you to quit smoking if you

wanted to?”

Smoking restrictions at home (es1_x) at baseline and follow-up (yes vs. no): based on the

response to the question “Which of the following best describe the smoking behaviours in your

home by the people who LIVE there? Responses of “No one smokes anywhere on the property”

and “No one smokes indoors at all” were classified as “yes”, and responses of “People smoke in

certain rooms only”, “People smoke except when young children are present”, “People smoke

anywhere in the home” and “People smoke in certain rooms except with kids present” were

classified as “no”.

Seeing an AD about stop smoking medication like the patch or gum at baseline and follow-

up (mm2_x) (yes vs. no): based on the responses to the question “In the past 30 days have you

seen or heard and ad about stop smoking mediation like the patch or gum?”

Self-perceived benefit from quitting at baseline (qb6a_0): based on the response to the

question “How much do you think you would benefit from health and other gains if you were to

quit smoking permanently in the next 6 months? Would you not benefit at all, benefit a little,

benefit quite a bit, or benefit a lot?” as “benefit quite a bit to benefit a lot” vs. “benefit little to

not at all”.

Main reason to quit smoking at baseline (qb8_0): based on the response to the question “What

is the main reason you plan to quit smoking?” categorized as “to reduce disease/risk/improve

health” and “illness/disability” vs. “other”.

Beliefs about stop smoking medications at baseline (qa10_0 and qa35_0): based on the

response to the question “Stop smoking medications make it easier to quit than trying to quit on

your own. Do you strongly agree, somewhat agree, somewhat disagree, or strongly disagree?”

categorized as “somewhat agree to strongly agree” vs. “somewhat disagree to strongly disagree”.

Beliefs about the cost of stop smoking medications at baseline (qa11_0): based on the

response to the question “The cost of stop smoking medications makes it default to use them. Do

you strongly agree, somewhat agree, somewhat disagree, or strongly disagree?” categorized as

“somewhat agree to strongly agree” vs. “somewhat disagree to strongly disagree”.

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Beliefs about hardness of getting stop smoking medications at baseline (qa12_0): based on

the response to the question “Stop smoking medications are hard to get. Do you strongly agree,

somewhat agree, somewhat disagree, or strongly disagree?” categorized as “somewhat agree to

strongly agree” vs. “somewhat disagree to strongly disagree”.

Concerns about side effects from stop smoking medications at baseline (qa14_0): based on

the response to the question “The risk of side effects from stop smoking medications concerns

you. Do you strongly agree, somewhat agree, somewhat disagree, or strongly disagree?”

categorized as “somewhat agree to strongly agree” vs. “somewhat disagree to strongly disagree”.

Ever use of NRT at baseline (yes vs. no): based on the response to the question at baseline

“Have you ever used nicotine patch to stop or reduce smoking?” Similar questions were asked

for gum, inhaler and lozenge use as well.

Other pharmacological quit aids at baseline and follow-up (yes vs. no): based on the

responses to the questions “In the past 6 months, did you use a pill prescribed by your doctor

called Zyban or bupropion?” (qa5a_x and qa5b_x), and “In the past 6 months, did you use a pill

prescribed by your doctor called Champix or Varenicline to help you stop smoking?” (qa34_x

and qa34b_x). The response of ‘yes’ to any of the above two questions was determined as ‘yes’

for “other pharmacological quit aids”.

Other quit aids (yes vs. no) at baseline and follow-up: based on the response to the questions

“In the past 6 months, have you used hypnosis, acupuncture, or laser therapy?” (qa6_x), “In the

past 6 months, have you used a self-help booklet or video, a website or a chat group?” (qa7_x),

“In the past 6 months, have been to group counselling or a group support program?” (qa8_x), “In

the past 6 months, have you seen a specialized addiction counsellor?” (qa9_x), “In the past 6

months, have you called the Ontario Smokers’ Helpline”(qa23_x), and “In the past 6 months,

have you taken part in a quit program?” The response of ‘yes’ to any of the above questions was

determined as ‘yes’ for “other quit aids”.

Number of serious quit attempts at follow-up (qb11a_x and qb11b_x): based on the responses

to the question “How many times have you made a serious attempt to quit smoking in the past 6

months? By serious, we mean that you made a conscious attempt to stay off cigarettes for good”

(qb11a_x) among those who tried to quit smoking completely, and to the question “In the past 6

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months, that is since [last interview time], how many times have you made a serious attempt to

quit before you were able to quit smoking? By serious, we mean that you made a conscious

attempt to stay off cigarettes for good.” (qb11b_x) among those who quit smoking completely at

follow-up.

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Appendix 5. Power Calculation

Table 38. Power calculation for short- and long-term quitting outcomes in the analysis for those who made a serious quit attempt

Outcome

NRT group

Samplesize†

N (%) of quitting outcome

Power 1‡

Power 2§

Power 3#

Quitting ≥ 1 month at Follow‐up 3

During any one follow‐up

Not using NRT 790 229 (29.0) >0.962 0.050 0.568

Using NRT <8 wks 464 91 (19.6)

Using NRT ≥8 wks 114 33 (29.0)

Not using patch 1023 277 (27.1) 0.787 0.237 0.720

Using patches <8 wks 281 54 (19.2)

Using patches ≥8 wks 64 22 (34.4)

Not using gum 1088 294 (27.0) 0.716 0.100 0.407

Using gum <8 wks 239 46 (19.3)

Using gum ≥8 wks 41 13 (31.7)

Quitting ≥ 12 months at Follow‐up 3

During any one follow‐up

Not using NRT 790 44 (5.6) 0.731 0.090 0.559

Using NRT <8 wks 464 12 (2.6)

Using NRT ≥8 wks 114 8 (7.0)

Not using patch 1023 50 (4.9) 0.457 0.458 0.775

Using patches <8 wks 281 7 (2.5)

Using patches ≥8 wks 64 7 (10.9)

Not using gum 1088 59 (5.4) ‐‐‐‐‐‐‐‐ ‐‐‐‐‐‐‐‐ ‐‐‐‐‐‐‐‐

Using gum <8 wks 239 ‐‐‐‐‐‐‐‐

Using gum ≥8 wks 41 ‐‐‐‐‐‐‐‐

Quit ≥ 1 month at any follow‐up

During any one follow‐up Not using NRT 980 505 (51.5) >0.999 0.966 >0.999 Using NRT <8 wks 510 192 (37.7) Using NRT ≥8 wks 100 71 (71.0) Not using patch 1227 598 (48.7) 0.762 >0.999 >0.999 Using patches <8 wks 306 123 (40.2) Using patches ≥8 wks 57 47 (82.5) Not using gum 1301 660 (50.7) 0.998 0.136 0.797 Using gum <8 wks 249 85 (34.1) Using gum ≥8 wks 40 23 (57.5)

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Quit ≥ 12 months at any follow‐up

During any one follow‐up before the quitting outcome Not using NRT 980 54 (5.5) 0.654 0.521 0.899 Using NRT <8 wks 510 15 (2.9) Using NRT ≥8 wks 100 11 (11.0) Not using patch 1227 63 (5.1) 0.407 0.692 0.882 Using patches <8 wks 306 9 (2.9) Using patches ≥8 wks 57 8 (14.0) Not using gum 1301 71 (5.5) 0.610 Using gum <8 wks 249 6 (2.4)

Using gum ≥8 wks 40 ‐‐‐‐‐‐‐‐

† Power calcula on was based on log‐transformed data for mean and SD (standard deviation), because the data were positively skewed. ‡ Power 1 for the comparison between not using NRT (patches or gum) and using NRT (patches or gum) <8 weeks. § Power 2 for the comparison between not using NRT (patches or gum) and using NRT (patches or gum) ≥8 weeks. # Power 3 for the comparison between using NRT (patches or gum) <8 weeks and using NRT (patches or gum) ≥8 weeks. ‐‐‐‐‐‐‐‐ Cell size <5, not reportable.

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Appendix 6. Assessment of Reliability of Measures for the Outcome and NRT Use

Agreement on Measures of the Outcome

Two questions were used to measure the reliability of the outcome measures of the current study.

They were 1) “Have you smoked a cigarette since we last spoke with you in [date of interview]?”

and 2) “How long ago was it that you last smoked a cigarette: was it one week or less, more than

one week but less than one month, 1 to 6 months ago; 7 to 12 months ago?” These two questions

were asked among the same respondents at the same interview.

Based on the three follow-up data, the agreement between these two questions among all

baseline current smokers is calculated as below.

Table 39. Agreement on cigarette smoking measures

Smoking

(SB29_x: Have you smoked a cigarette

since we last spoke with you?)

Smoking

(SB3_x: How long ago was it that

you last smoked a cigarette?)

Yes No Total

Yes 1379 2 1381

No 4 285 289

Total 1383 287 1670

Chance expected agreement = (1381 x 1383 + 285x 287) / 16702 = 0.714

Observed agreement = (1379+ 285) / 1670 = 0.996

Kappa = (0.996 – 0.714) / (1 – 0.714) = 0.986.

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Agreement on Measures of NRT Use

Two questions on patch, gum, inhaler and lozenge use as well as their use duration in the OTS

longitudinal study were used to measure the reliability of NRT use measures. Based on the

answers to these two questions of all baseline current smokers in the OTS longitudinal study for

all three follow-ups (one might use NRT three times with three duration), the reliability of NRT

measures was estimated below.

Table 40. Agreement on NRT use measures

NRT use

(any NRT use at follow‐up)

NRT use

(Duration of NRT use at follow‐up)

Yes No Total

Yes 1240 24 1264

No 4 8473 8477

Total 1244 8497 9741

Chance expected agreement = (1264 x 1244 + 8497 x 8473) / 97412 = 0.775

Observed agreement = (1240+ 8473) / 9409 = 0.997

Kappa = (0.997 – 0.775) / (1 – 0.775) = 0.987.

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Appendix 7. Association between NRT Use (yes vs. no) and Smoking Cessation of Poisson Regression

Table 41. Crude and adjusted Poisson regression analyses of the aassociations between quit aid use (yes vs. no) and quitting short- (≥1 month) and long-term (≥12 months) in the current study, OTS longitudinal study 2005-2009

Crude analysis Adjusted analysis‡ Outcome Quit aid RR (95% CI) † P value RR (95% CI) † P value Quit ≥1 month at the end of 18 months of follow-up

NRT No Referent Referent Yes 0.74 (0.61-0.90) 0.0019 0.87 (0.71-1.05) 0.1538

Patches No Referent Referent Yes 0.81 (0.65-1.02) 0.0692 0.96 (0.76-1.20) 0.6909 Gum No Referent Referent Yes 0.78 (0.61-1.00) 0.0483 0.85 (0.66-1.08) 0.1882 Quit ≥12 months at the end of 18 months of follow-up

NRT

No Referent Referent Yes 0.62 (0.37-1.04) 0.0715 0.69 (0.41-1.17) 0.1691 Patches No Referent Referent Yes 0.83 (0.46-1.48) 0.5296 0.93 (0.52-1.68) 0.8210 Gum No Referent Referent Yes 0.33 (0.13-0.81) 0.0160 0.35 (0.14-0.87) 0.0236 Quit ≥1 month at any period of follow-up

NRT No Referent Referent Yes 0.80 (0.66-0.97) 0.0239 0.94 (0.77-1.14) 0.5034

Patches No Referent Referent Yes 0.85 (0.68-1.06) 0.1483 0.99 (0.79-1.25) 0.9518 Gum No Referent Referent Yes 0.88 (0.69-1.13) 0.3235 0.95 (0.74-1.21) 0.6546 Quit ≥12 months at any period of follow-up

NRT

No Referent Referent Yes 0.71 (0.42-1.19) 0.1903 0.80 (0.47-1.34) 0.3904 Patches No Referent Referent Yes 0.91 (0.51-1.62) 0.7484 1.03 (0.57-1.85) 0.9231 Gum No Referent Referent Yes 0.38 (0.15-0.94) 0.0360 0.40 (0.16-1.00) 0.0488 † RR, rela ve risk; CI, confidence interval. ‡ Adjusted for daily smoking and number of cigarettes smoked per day.

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Appendix 8. NRT Use Patterns in the Analysis for Those Who Made A Serious Quit Attempt

Table 42. Quit aid use patterns among those who made serious quit attempts at follow-up, OTS longitudinal study 2005-2009

Quit aid No. of users % among overall sample % among users Any aid† (n = 1,590) (n = 986) Non 604 38.0% -------- NRT 657 41.3% 66.6% Other quit methods‡ 364 22.9% 36.9% Behavioral support§ 290 18.2% 29.4% Bupropion SR or varenicline 278 17.5% 28.2% NRT and other quit methods‡ 208 13.1% 21.1% NRT and behavioral support 161 10.1% 16.3% NRT and bupropion SR or varenicline 121 7.6% 12.3% NRT (n = 1,590) (n = 657) Non 933 58.7% -------- Patch alone 276 17.4% 42.0% Gum alone 213 13.4% 32.4% Patch and gum 75 4.7% 11.4% Patch and other NRT products# 27 1.7% 4.1% Gum and other NRT products# 23 1.5% 3.5% Patch, gum and other NRT products# 10 0.6% 1.5% Other NRT products# 33 2.1% 5.0% † Percentage for any quit aid were inclusive, i.e., the sum of percentages over 100%. ‡ Other quit methods including self‐help materials, acupuncture, hypnosis, etc. § Behavioral support, including counseling, using helpline and taking parting in quit programs. # Other NRT products, including inhaler and lozenges.

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Appendix 9. Abstract for the 7th National Conference on Tobacco or Health

Abstract

Abstract Stream

Research Abstract

Title of Presentation

Who used NRTs for recommended length and who did not? A longitudinal study of Ontario smokers

Abstract Purpose: To investigate factors associated with NRT use duration in a general population of smokers. Relevance/Context: Nicotine replacement therapy (NRT) doubles successful quitting in clinical trials. However, the effects of NRT in general population smokers have been inconsistent. One possible reason is that more than half of NRT users do not comply with recommended length of 8-12 weeks. No studies have examined factors associated with NRT use duration. METHODS: A representative sample of Ontario smokers who quit or tried to quit smoking during follow-up, from the Ontario Tobacco Survey longitudinal study was used to investigate characteristics of smokers in relation to their NRT use duration (<8 weeks vs. ≥8 weeks). Logistic regression analysis was conducted to determine what factors were associated with longer use duration. RESULTS: Among the 1,754 baseline current smokers who quit or tried to quit smoking at follow-up, 30% (n=533) used NRT<8 weeks and 6% (n=108) used NRT≥8 weeks, while the majority (64%) did not use NRT. Among NRT users, the median duration was 14 days. For NRT users, intention to quit in next 30 days was associated with a higher likelihood of using NRT≥8 weeks (odds ratio (OR) 1.86, 95% confidence interval (CI) 1.19-2.93). Perceiving the cost of quit medications too high (OR 0.60, 95% CI 0.39-0.92) and using pipe or snus (OR 0.38, 95% CI 0.16-0.89) were associated with a lower likelihood of using NRT≥8 weeks, after adjusting for socio-demographic characteristics, tobacco dependence, previous quit behaviors, self-perceived addiction, social and environmental factors for quitting, and other quit aid use. CONCLUSIONS: In this representative sample of Ontario smokers, the majority did not use NRT when attempting to quit. Among NRT users, the median duration was strikingly below the recommended length. Only a

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small proportion of smokers reached the minimum recommended length. Increasing intention to quit, improving the understanding that quit medications are cheaper than cigarettes, and reducing pipe or snus use among cigarette smokers will likely increase NRT compliance with recommended length and improve cessation outcomes.

Learning Objectives

Learning Objective 1: Articulate the recommended length of NRT use

Learning Objective 2: Discuss the length of NRT use among Ontario smokers and identify three indicators associated with recommended length of NRT use

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Appendix 10. Sensitivity Analysis

10.1 Questions Used to Identify Participants in the Sensitivity analysis

Respondents in the OTS panel survey were included in this sensitivity analysis if they responded

“Yes” to the question “SB14_X” “At any time during the past 6 months, did you change your

smoking behaviours with the intention of quitting or reducing the amount you smoke?”, “Yes” to

the question “SB16_X” “In the past 6 months, did you try to go whole days without smoking?”,

“Yes” to the question “SB18_x” “On the days that you did smoke, did you reduce the number of

cigarettes you usually smoke?”, “Yes” to the question “SB20_x” “Did you try not to smoke the

whole cigarette?”, and those who made a serious attempt to quit at follow-up among baseline

smokers.

Figure 6. Flow diagram for the questions in the OTS study to identify those who made a serious attempt to quit and those who reduced smoking at follow-up, sensitivity analysis

at follow-up

SB13_XCompared to 6 months ago, that is since [last interview time], would you say that you are now smoking … 01 – the same as you were smoking GOTO SB14_X 02 – more than you were smoking OR GOTO SB14_X 03 – less than you were smoking GOTO SB15_X 04 – Quit completely [DO NOT READ] GOTO QB11b_X 06 – Don’t know GOTO SB14_X 09 – Refused GOTO SB14_X

SB14_XAt any time during the past 6 months, did you change your smoking behaviours with the intention of quitting or reducing the amount you smoke? [DO NOT READ CATEGORIES] 01 – Yes GOTO SB15_X 02 – No GOTO DSB23_X 06 – Don’t know GOTO SB15_X 09 – Refused GOTO SB15_X

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SB15_XHow did you change your smoking behaviour when you were trying to reduce the amount you smoke in the past 6 months?...” Did you try to quit smoking completely? [If necessary, remind respondent “during the past 6 months”] 01 – Yes GOTO QB11a_X 02 – No GOTO SB16_X 06 – Don’t know GOTO SB16_X 09 – Refused GOTO SB16_X

SB16_XIn the past 6 months, did you try to go whole days without smoking? [DO NOT READ CATEGORIES] 01 – Yes GOTO SB17_X 02 – No GOTO SB18_X 06 ‐ Don’t know GOTO SB18_X 09 – Refused GOTO SB18_X

SB18_XIf SB16_X=01 SHOW: “On the days that you did smoke…” Did you reduce the number of cigarettes you usually smoke? [DO NOT READ CATEGORIES] 01 – Yes GOTO SB19_X 02 – No GOTO SB20_X 06 ‐ Don’t know GOTO SB20_X 09 – Refused GOTO SB20_X

SB20_XDid you try not to smoke the whole cigarette? [DO NOT READ CATEGORIES] 01 – Yes 02 – No 06 ‐ Don’t know 09 – Refused

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10.2 Flow Diagram in the Sensitivity Analysis

Figure 7. Flow diagram for analysis of longitudinal respondents at 6-, 12- and 18-month follow-ups with valid data on smoking at baseline and follow-up, sensitivity analysis

Baseline recent smokers (Complete data)

N = 4,504


who made serious quit attempts or reduced smoking at follow‐ups one, two, or three [i.e.,

(2695‐417)/2695 = 85%]

Lost to follow‐up at the end of 18 months N = 417 (retention rate†: 85%)

Excluded: Non‐current smokers at baseline 1. < 100 cigarettes/lifetime (n = 146) 2. Former smokers (not smoked in the past 30

days; n = 291) 3. Smoking status not known (n = 3)

Excluded at follow‐up: Did not make a serious quit attempt or reduce smoking at follow‐ups one, two, or three (n =1,369)


Total N = 2,278

Those who made a serious quit attempt or reduced smoking at follow‐ups one, two, or

three; Total N = 2,695



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10.3 Associations of NRT Quit Aid Use Duration and Quitting Outcomes of the Sensitivity Analysis

Table 43. Crude and adjusted Poisson regression analyses in the sensitivity analysis: association between any NRT use duration and short-term abstinence (continuous quitting ≥1 month) at the end of 18 months of follow-up among baseline smokers who made serious quit attempts or reduced smoking at follow-up and were re-interviewed 18 months later (n=2,278), OTS longitudinal study 2005-2009

Quit aid Model Sample size

n (%) % of quit ≥1 month

Crude RR† Adjusted RR†‡

(95% CI)§ P

value

(95% CI)§ P

value Two groups for NRT use duration, based on the longest use at any one follow-up Non-use 1 1558 (68.4) 15.8% Referent Referent NRT use 720 (31.6) 17.6% 1.12 (0.92-1.36) 0.27 1.29 (1.03-1.62) 0.029 Three groups for NRT use duration, based on the longest use at any one follow-up Non-use 2 1558 (68.4) 15.8% Referent Referent <8 weeks 592 (26.0) 15.7% 0.99 (0.80-1.24) 0.96 1.15 (0.90-1.47) 0.27 ≥8 weeks 128 (5.6) 26.6% 1.68 (1.23-2.29) 0.0010 2.03 (1.45-2.86) <0.0001 <8 weeks 3# 592 (26.0) 15.7% Referent Referent ≥8 weeks 128 (5.6) 26.6% 1.69 (1.20-2.39) 0.0027 1.77 (1.26-2.50) 0.0011 Four groups for NRT use duration, based on the longest use at any one follow-up (best fit model) Non-use 4 1558 (68.4) 15.8% Referent Referent <4 weeks 480 (21.1) 13.5% 0.86 (0.67-1.11) 0.24 1.01 (0.77-1.33) 0.92 ≥4-<8 weeks 112 (4.9) 25.0% 1.58 (1.13-2.23) 0.0080 1.68 (1.15-2.44) 0.0068 ≥8 weeks 128 (5.6) 26.6% 1.68 (1.23-2.29) 0.0010 2.04 (1.45-2.86) <0.0001 No interaction effects were found for any variables with NRT use duration † RR, rela ve risk. ‡ Adjusted for baseline variables of daily smoking, cigarettes per day smoked, HSI, life time quit attempts, self‐perceived addiction, self‐perceived easiness of quitting, self‐perceived confidence of quitting, self‐perceived benefit from quitting, main quit reason to improve health and reduce disease risk, home smoking restrictions, ever use of NRT, and follow‐up variables of number of quit attempts and use of bupropion SR or varenicline.

§ CI, confidence interval. # The model analysis included all three groups for NRT use duration; only the results for using NRT <8 weeks and ≥8 weeks are presented here.

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Table 44. Crude and adjusted Poisson regression analyses in the sensitivity analysis: association between patch use duration and short-term abstinence (continuous quitting ≥1 month) at the end of 18 months of follow-up among baseline smokers who made serious quit attempts or reduced smoking at follow-up and were re-interviewed 18 months later (n=2,278), OTS longitudinal study 2005-2009



Crude RR† Adjusted RR†‡ (95% CI)§ P

value (95% CI)§ P

value Two groups for patch use duration, based on the longest use at any one follow-up Non-use 1 1888 (82.9) 15.6% Referent Referent Patch use 390 (17.1) 20.3% 1.30 (1.04-1.63) 0.0209 1.54 (1.20-1.98) 0.0007 Three groups for patch use duration, based on the longest use at any one follow-up Non-use 2 1888 (82.9) 15.6% Referent Referent <8 weeks 321 (14.1) 17.5% 1.12 (0.86-1.45) 0.3920 1.31 (0.98-1.73) 0.0662 ≥8 weeks 69 (3.0) 33.3% 2.14 (1.51-3.04) <0.0001 2.78 (1.91-4.04) <0.0001 <8 weeks 3# 321 (14.1) 17.5% Referent Referent ≥8 weeks 69 (3.0) 33.3% 1.91 (1.27-2.88) 0.0020 2.13 (1.40-3.24) 0.0004 Four groups for patch use duration, based on the longest use at any one follow-up (best fit model) Non-use 4 1888 (82.9) 15.6% Referent Referent <4 weeks 253 (11.1) 15.4% 0.99 (0.73-1.35) 0.9484 1.18 (0.85-1.64) 0.3184 ≥4-<8 weeks 68 (3.0) 25.0% 1.61 (1.05-2.46) 0.0290 1.72 (1.08-2.73) 0.0222 ≥8 weeks 69 (3.0) 33.3% 2.14 (1.51-3.04) <0.0001 2.78 (1.91-4.04) <0.0001 No interaction effects were found for any variables with patch use duration † RR, rela ve risk. ‡ Adjusted for baseline variables of daily smoking, cigarettes per day smoked, HSI, life time quit attempts, making quitting attempts in 12 months prior to baseline, self‐perceived addiction, self‐perceived easiness of quitting, self‐perceived benefit from quitting, main quit reason to improve health and reduce disease risk, home smoking restrictions, ever use of NRT, and follow‐up variables of number of quit attempts and use of bupropion SR or varenicline. For the models with three and four groups for NRT use duration, an additional baseline variable of someone making quitting difficult was also controlled for.

§ CI, confidence interval. # The model analysis included all three groups for patch use duration; only the results for using patches <8 weeks and ≥8 weeks are presented here.

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Table 45. Crude and adjusted Poisson regression analyses in the sensitivity analysis: association between gum use duration and short-term abstinence (continuous quitting ≥1 month) at the end of 18 months of follow-up among baseline smokers who made serious quit attempts or reduced smoking at follow-up and were re-interviewed 18 months later (n=2,278), OTS longitudinal study 2005-2009



Crude RR† Adjusted RR†‡ (95% CI)§ P

value (95% CI)§ P

value Two groups for gum use duration, based on the longest use at any one follow-up Non-use 1 1902 (83.5) 16.5% Referent Referent Gum use 376 (16.5) 15.7% 0.95 (0.74-1.23) 0.70 0.95 (0.73-1.25) 0.72 Three groups for gum use duration, based on the longest use at any one follow-up Non-use 2 1902 (83.5) 16.5% Referent Referent <8 weeks 328 (14.4) 14.0% 0.85 (0.64-1.13) 0.26 0.89 (0.66-1.20) 0.45 ≥8 weeks 48 (2.1) 27.1% 1.64 (1.02-2.64) 0.041 1.32 (0.81-2.18) 0.27 <8 weeks 3# 328 (14.4) 14.0% Referent Referent ≥8 weeks 48 (2.1) 27.1% 1.93 (1.13-3.30) 0.016 1.49 (0.86-2.56) 0.16 Four groups for gum use duration, based on the longest use at any one follow-up (best fit model) Non-use 4 1902 (83.5) 16.5% Referent Referent <4 weeks 291 (12.8) 13.4% 0.81 (0.60-1.11) 0.19 0.86 (0.62-1.18) 0.34 ≥4-<8 weeks 37 (1.6) 18.9% 1.15 (0.58-2.25) 0.69 1.14 (0.57-2.26) 0.71 ≥8 weeks 48 (2.1) 27.1% 1.64 (1.02-2.64) 0.041 1.32 (0.81-2.17) 0.27 No interaction effects were found for any variables with gum use duration † RR, rela ve risk. ‡ Adjusted for baseline variables of education, daily smoking, cigarettes per day smoked, HSI, self‐perceived addiction, self‐perceived easiness of quitting, ever use of NRT, and follow‐up variables of number of quit attempts, and use of other NRT products without gum. An additional baseline variable of self‐perceived benefit from quitting was controlled for in the models with NRT use duration with two and three groups, and an extra follow‐up variable of use of bupropion SR or varenicline was also controlled for in the model with NRT used duration of two groups.

§ CI, confidence interval. # The model analysis included all three groups for gum use duration; only the results for using gum <8 weeks and ≥8 weeks are presented here.

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Table 46. Crude and adjusted Poisson regression analyses in the sensitivity analysis: association between any NRT use duration and short-term abstinence (continuous quitting ≥1 month) during any period of follow-up among baseline smokers who made serious quit attempts or reduced smoking at follow-up (n=2,695), OTS longitudinal study 2005-2009



Crude RR† Adjusted RR†‡ (95% CI)§ P value (95% CI)§ P value

Two groups for NRT use duration, based on the sum of all NRT use durations before the outcome Non-use 1 1938 (71.9) 35.7% Referent Referent NRT use 757 (28.1) 38.3% 1.07 (0.96-1.20) 0.20 1.16 (1.03-1.30) 0.017 Three groups for NRT use duration, based on the sum of all NRT use durations before the outcome Non-use 2 1938 (71.9) 35.7% Referent Referent <8 weeks 630 (23.4) 32.7% 0.92 (0.81-1.04) 0.17 1.00 (0.87-1.14) 0.96 ≥8 weeks 127 (4.7) 66.1% 1.85 (1.61-2.13) <0.0001 2.06 (1.75-2.41) <0.0001 <8 weeks 3# 630 (23.4) 32.7% Referent Referent ≥8 weeks 127 (4.7) 66.1% 2.02 (1.71-2.39) <0.0001 2.06 (1.73-2.47) <0.0001 Four groups for NRT use duration, based on the sum of all NRT use durations before the outcome (best fit model) Non-use 4 1938 (71.9) 35.7% Referent Referent <4 weeks 501 (18.6) 28.7% 0.81 (0.69-0.94) 0.0047 0.89 (0.76-1.04) 0.14 ≥4-<8 weeks 129 (4.8) 48.1% 1.35 (1.11-1.63) 0.0021 1.38 (1.13-1.68) 0.0015 ≥8 weeks 127 (4.7) 66.1% 1.85 (1.61-2.13) <0.0001 2.03 (1.73-2.38) <0.0001 No interaction effects were found for any variables with NRT use duration † RR, rela ve risk. ‡ Adjusted for baseline variables of daily smoking, cigarettes per day smoked, self‐perceived addiction, self‐perceived easiness of quitting, self‐perceived confidence of quitting, self‐perceived benefit from quitting, main quit reason to improve health and reduce disease risk, home smoking restrictions, ever use of NRT, and follow‐up variables of number of quit attempts, use of bupropion SR or varenicline and time in the study. For the models with two and four groups for NRT use duration, HSI was controlled for too. An additional variable of education for the model with four groups of NRT use duration was controlled too.

§ CI, confidence interval. # The model analysis included all three groups for NRT use duration; only the results for using NRT <8 weeks and ≥8 weeks are presented here.

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Table 47. Crude and adjusted Poisson regression analyses in the sensitivity analysis: association between patch use duration and short-term abstinence (continuous quitting ≥1 month) during any period of follow-up among baseline smokers who made serious quit attempts or reduced smoking at follow-up (n=2,695), OTS longitudinal study 2005-2009




Two groups for patch use duration, based on the sum of use durations during follow-up Non-use 1 2280 (84.6) 35.2% Referent Referent Patch use 415 (15.4) 43.4% 1.23 (1.09-1.39) 0.0009 1.37 (1.20-1.56) <0.0001 Three groups for patch use duration, based on the sum of use durations during follow-up Non-use 2 2280 (84.6) 35.2% Referent Referent <8 weeks 344 (12.8) 36.3% 1.03 (0.89-1.20) 0.67 1.16 (0.99-1.35) 0.064 ≥8 weeks 71 (2.6) 77.5% 2.20 (1.92-2.53) <0.0001 2.49 (2.09-2.95) <0.0001 <8 weeks 3# 344 (12.8) 36.3% Referent Referent ≥8 weeks 71 (2.6) 77.5% 2.13 (1.77-2.57) <0.0001 2.15 (1.75-2.65) <0.0001 Four groups for patch use duration, based on the sum of use durations during follow-up (best fit model) Non-use 4 2280 (64.6) 35.2% Referent Referent <4 weeks 269 (10.0) 30.1% 0.87 (0.71-1.04) 0.10 0.97 (0.80-1.17) 0.74 ≥4-<8 weeks 75 (2.8) 58.7% 1.67 (1.37-2.03) <0.0001 1.84 (1.49-2.27) <0.0001 ≥8 weeks 71 (2.6) 77.5% 2.20 (1.92-2.53) <0.0001 2.49 (2.10-2.96) <0.0001 No interaction effects were found for any variables with patch use duration † RR, relative risk. ‡ Adjusted for baseline variables of daily smoking, cigarettes per day smoked, HSI, making quit attempts in 12 months prior to baseline, self‐perceived addiction, self‐perceived easiness of quitting, self‐perceived benefit from quitting, main quit reason to improve health and reduce disease risk, home smoking restrictions, ever use of NRT, and follow‐up variables of number of quit attempts, use of bupropion SR or varenicline. For the models with two and three groups for patch use duration, an additional baseline variable of self‐perceived confidence of quitting was controlled too. For the models with three and four groups for patch use duration, an additional follow‐up variable of time staying the study was controlled for too.

§ CI, confidence interval. # The model analysis included all three groups for patch use duration; only the results for using patches <8 weeks and ≥8 weeks are presented here.

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Table 48. Crude and adjusted Poisson regression analyses in the sensitivity analysis: association between gum use duration and short-term abstinence (continuous quitting ≥1 month) during any period of follow-up among baseline smokers who made serious quit attempts or reduced smoking at follow-up (n=2,695), OTS longitudinal study 2005-2009




Two groups for gum use duration, based on the sum of use durations at follow-up Non-use 1 2311 (85.8) 37.2% Referent Referent Gum use 384 (14.2) 32.0% 0.86 (0.74-1.01) 0.060 0.84 (0.72-0.99) 0.032 Three groups for gum use duration, based on the sum of use durations at follow-up Non-use 2 2311 (85.8) 37.2% Referent Referent <8 weeks 334 (12.4) 28.4% 0.76 (0.64-0.91) 0.0032 0.77 (0.64-0.92) 0.0040 ≥8 weeks 50 (1.9) 56.0% 1.51 (1.17-1.94) 0.0014 1.28 (0.97-1.69) 0.080 <8 weeks 3# 334 (12.4) 28.4% Referent Referent ≥8 weeks 50 (1.9) 56.0% 1.97 (1.46-2.65) <0.0001 1.67 (1.21-2.29) 0.0016 Four groups for gum use duration, based on the sum of use durations at follow-up (best fit model) Non-use 4 2311 (85.8) 37.2% Referent Referent <4 weeks 298 (11.1) 27.9% 0.75 (0.62-0.91) 0.0030 0.75 (0.62-0.91) 0.0031 ≥4-<8 weeks 36 (1.3) 33.3% 0.90 (0.56-1.43) 0.65 0.89 (0.57-1.39) 0.60 ≥8 weeks 50 (1.9) 56.0% 1.51 (1.17-1.94) 0.0014 1.29 (0.98-1.70) 0.069 No interaction effects were found for any variables with gum use duration † RR, rela ve risk. ‡ Adjusted for baseline variables of education, daily smoking, making quit attempts 12 months prior to baseline, self‐perceived addiction, self‐perceived easiness of quitting, self‐perceived benefit from quitting, main quitting reason being reducing disease risk or improving health, ever use of NRT, beliefs of quit medications making quitting easier, and follow‐up variables of number of quit attempts, use of behavioural support, use of other quitting methods, and use of other NRT products without gum. For the model with two groups for gum use duration, additional baseline variables of number of cigarettes smoked, HSI, self‐perceived confidence of quitting were controlled for too. For the model with three groups for gum use duration, additional baseline variables of number of cigarettes smoked and self‐perceived confidence of quitting were controlled for too.

§ CI, confidence interval. # The model analysis included all three groups for gum use duration; only the results for using gum <8 weeks and ≥8 weeks are presented here.

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Appendix 11. Examination of Representativeness

Table 49. Representativeness of the OTS sample to the CCHS 2007 survey population

OTS smokers at baseline

(un‐weighted)

OTS smokers at baseline (weighted)

Ontario smokers in the CCHS 2007 survey

Age (years) 18‐29 (%) 20.5% 26.8% 26.2% 30‐64 (%) 71.5% 65.6% 67.1% 65+ (%) 8.0% 7.5% 6.8% Sex Female (%) 54.8% 46.7% 43.1% Education <High school (%) 17.4% 15.1% 18.3% High school (%) 31.3% 32.1% 22.3% Some post‐secondary (%) 11.4% 10.5% 9.8% Post‐secondary graduation (%) 39.9% 42.3% 49.7% Marital status Never married (%) 23.3% 26.7% 28.7% Married/common law (%) 53.4% 57.5% 56.5% Widowed/separated/divorced (%) 23.3% 15.8% 14.8% Self‐perceived health Poor‐Fair (%) Excellent (%) 19.7% 17.8% 16.3% Good‐Excellent (%) 80.3% 82.2% 83.7% Smoking status Daily (%) 82.2% 78.6% 83.0% Occasionally (%) 17.8% 21.4% 17.0% Cigarettes per day – mean (SE) 15.7 (10.3)† 14.3 (0.23) 12.6 (0.15) 1‐10 cigarettes/day (%) 32.9% 36.8% 49.6% 11‐20 cigarettes/day (%) 41.7% 40.2% 34.2% 21+ cigarettes/day (%) 25.4% 23.0% 16.2% Heaviness of smoking index‡ Low (%) 24.9% 29.1% 25.4% Moderate (%) 42.0% 40.6% 59.9% High (%) 33.1% 30.2% 14.7% Attempt to quit smoking within the next six months (%)

38.9% 37.4% 61.3%

Attempt to quit smoking within the next 30 days (%)

13.8% 13.7% 26.1%

Tried to quit smoking for at least 24 hours or made a serious quit attempt in the past 12 months (%)

34.2% 36.5% 49.1%

† Number in brackets is the standard deviation (SD). ‡ HSI calculated based on the CTUMS 2007 data for Ontario, because information on time to the first cigarette

after waking was not available in the CCHS 2007 data for Ontario.

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Appendix 12. Analyses for Smokers with Complete Data in the Analysis for Those Who Made A Serious Quit Attempt

In this additional analysis, the associations between use duration of NRT quit aids and quitting

outcomes at the end of 18 months were examined among smokers who had complete data for

baseline and all three follow-ups (i.e., no missing data for any follow-up). This way, smokers had

equal opportunity to provide data. For the short-term quitting outcome, those who made a serious

quit attempt at follow-up one or two and were re-interviewed at follow-up three were included in

analysis. This meant that even if some smokers made a serious quit attempt toward the end of

follow-up two, they would still have at least six months of follow-up after making the serious

quit attempt. These smokers (n=1,014) were eligible sample for the short-term quitting outcome

(continuous quitting for at least one month). For the long-term quitting outcome, those who made

a serious quit attempt at follow-up one and had complete data for all three follow-ups were

included in analysis. This meant that even if some smokers made a serious quit attempt toward

the end of follow-up one, they would still have at least 12 months of follow-up after making the

serious quit attempt. These smokers (n=700) were eligible sample for the long-term quitting

outcome (continuous quitting for at least 12 months).

The results show that those who used any NRT, patches, or gum <8 weeks were less likely to

quit short-term or long term. Only using patches ≥8 weeks was associated with a higher

likelihood of short- and long-term quitting at the end of 18 months of follow-up. Using gum even

for eight weeks or more was not associated with a higher likelihood of quitting short- or long-

term. Findings from the analysis with complete data are similar to those with incomplete data.

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Table 50. Adjusted RRs from Poisson regression for quitting outcomes at the end of 18 months of follow-up among those who made a serious quit attempt at follow-up with complete follow-up data

Short-term abstinence† (n=1,014)

Long-term abstinence‡ (n=700)

NRT Adjusted RR (95% CI)

P value Adjusted RR (95% CI)

P value

Any NRT Non-use Referent Referent Use<8wks 0.90 (0.69-1.17) 0.43 0.51 (0.28-0.93) 0.03 use≥8 wks 1.26 (0.86-1.85) 0.24 1.50 (0.75-2.99) 0.25 Patches Non-use Referent Referent Use<8wks 0.89 (0.64-1.23) 0.47 0.59 (0.27-1.28) 0.18 use≥8 wks 1.66 (1.08-2.54) 0.021 3.03 (1.49-6.16) 0.002 Gum use Non-use Referent Referent Use<8wks 0.84 (0.61-1.15) 0.28 0.33 (0.12-0.88) 0.028 use≥8 wks 1.16 (0.63-2.10) 0.64 0.39 (0.06-2.80) 0.35

Note: adjusted for the same confounding factors as in the analysis including those with incomplete data.

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Appendix 13. Comparison between Smokers Using Gum Only and Using Patches Only in the Current Study

The tables below compare the characteristics between smokers who used gum only and using

patches only but not other NRT products, and between smokers who used gum ≥8 weeks and

used patches ≥8 weeks but not other NRT products, among those who made at least one serious

quit attempt at follow-up in the current study.

Those who used gum only were very similar to those who used patches only, with regard to

socio-demographic characteristics and tobacco dependence variables, except that those who used

patches only had slightly higher proportions of people with <high school education and daily

smoking than those who used gum only (17.9% vs13.8% for <high school education and 89.2%

vs. 83.3% for daily smoking; both in favor of gum only users for quitting smoking). Other

significant differences included self-perceived addiction (very addicted: 84.0% in patch only

users vs. 74.9% in gum only users); home smoking restrictions (41.8% in patch only users vs.

51.7% in gum only users); beliefs about medications for cessation (making quit easier: 84.7% in

patch only users vs. 76.4% in gum only users); and using other tobacco products at follow-up

(9.3% in patch only users vs. 19.2% in gum only users). All these factors except for the last two

were in favor of gum only users for quitting smoking (Table 51).

Similar to the comparison between gum only users and patch only users, there were no

differences in socio-demographic characteristics and tobacco dependence variables between

smokers using gum only ≥8 weeks and using patches only ≥8 weeks. The only significant

difference was a socio-environmental factor of someone making quitting difficult (57.4% in

those using patches only ≥8 weeks and 25.9% in those using gum only ≥8 weeks, in favor of

those using gum only ≥8 weeks for quitting smoking). Those who used patches only ≥8 weeks

(mean = 16.9 cigarettes/day) smoked slightly more cigarettes per day than those who used gum

only ≥8 weeks (mean = 15.0 cigarettes/day) (p=0.075); and the proportion of ever use of

behavior support was higher among those who used gum only ≥8 weeks (29.6%) than among

those who used patches only ≥8 weeks (11.1%) (p=0.059); both in favor of those who used gum

only ≥8 weeks for quitting smoking (Table 52).

218

Table 51. Comparison between smokers using gum and patches only (not using other NRT products) among those who made at least one serious quit attempt at follow-up, OTS longitudinal study 2005-2009

Using gum only (N=203 )

Using patches only (N=268 )

P value Timing Characteristics % %

Baseline Socio‐demographic characteristics Age (years) Mean (SD)† 44.1 (12.7) 45.3 (13.3) Median (min‐max) 46.0 (18‐77) 46.0 (18‐82) 18‐24 9.5 9.0 0.32 25‐39 24.0 22.2 40‐54 47.5 44.7 55‐64 14.0 17.7 65+ 5.0 6.4 Sex Female 58.6 64.9 0.16 Education <High school 13.8 17.9 0.045 High school 28.1 33.2 Some post‐secondary 12.8 11.6 Post‐secondary graduation 43.8 36.2 Marital status Never married 16.7 16.4 0.64 Married/common law 57.6 56.0 Widowed/separated/divorced 25.6 27.6 General health Self‐perceived health Good – Excellent 75.9 76.1 0.95 Poor – Fair 24.1 23.9 Nicotine dependence Smoking status Daily 83.3 89.2 0.062 Occasionally 16.8 10.8 Cigarettes per day Mean (SD)† 15.2 (9.0) 17.1 (9.4) Median (min‐max) 15.0 (1‐50) 15.0 (1‐50) 1‐10 cigarettes/day 34.5 26.5 0.15 11‐20 cigarettes/day 38.4 44.0 21+ cigarettes/day 27.1 29.5 Heaviness of smoking index Low 34.2 30.7 0.75 Moderate 48.9 54.0 High 16.9 15.3 Using other tobacco (e.g., cigar,

snus) 9.9 6.7 0.22 Past quit history

219

# of lifetime quit attempts Mean (SD)† 4.6 (6.1) 4.6 (8.3) Median (min‐max) 3.0 (0‐50) 3.0 (0‐100) Tried to quit in the last 12 months 36.5 37.7 0.78 Planned the most recent quit

attempt 22.2 21.6 0.89 Intention to quit Intention to quit Within the next 30 days 24.6 28.4 0.29 Within 1‐6 months 36.5 37.3 Beyond next 6 months 23.2 23.1 No intention to quit 11.3 5.6 Not applicable 4.4 4.6 A firm date for the planned quit

attempt 13.8 17.5 0.27 Beliefs about addiction and quitting Self‐perceived addiction Not at all to somewhat addicted 25.1 16.0 0.015 Very addicted 74.9 84.0 Self‐perceived easiness to quit Somewhat to very easy 8.9 6.3 0.30 Somewhat to very hard 91.1 93.7 Self‐perceived confidence to quit

completely Fairly to very confident 53.2 60.1 0.14 Not very to not at all confident 46.8 39.9 Motivational variables for quitting Perceived benefit from quitting Quite a lot to a lot 87.2 89.9 0.35 Not at all to little 12.8 10.1 Main reason for planning to quit To reduce disease risk or improve

health 42.4 44.8 0.60 Social‐environmental factors for


support quitting 82.8 82.1 0.85 Someone making quitting difficult 46.3 48.5 0.64 Other household member(s)

smoking 3.9 7.1 0.15 No indoor smoking at home 51.7 41.8 0.032 Seeing or hearing an ad about stop

smoking medications such as nicotine patch and gum 72.4 71.6 0.85

220

Quit aids Ever use of quit aid patterns Ever used NRT‡ to quit smoking 78.3 84.0 0.12 Ever used other pharmaceutical

aids§ 36.5 44.8 0.069 Ever used behaviour support¶ 20.2 15.3 0.17 Ever used other quit methods†† 46.8 41.0 0.21 Beliefs about quit medications Using medications making quitting

easier 76.4 84.7 0.022 Difficult to use medications due to

the cost 38.9 46.6 0.094 Hard to get quit medications 11.8 8.6 0.25 Concerning the side effects 43.4 36.2 0.12

Follow‐up

Quit aids at follow‐up Other pharmaceutical aids§ 18.2 17.5 0.85

Behavioural support¶ 22.2 26.5 0.28 Other quit methods†† 35.0 29.9 0.24 Using other tobacco

(e.g., cigar, snus) at FU 19.2 9.3 0.0020 # of quit attempts Mean (SD)† 2.7 (4.2) 2.4 (3.5) Median (min‐max) 1.0 (1.0‐40) 1.0 (1‐41)

† SD, standard deviation for un‐weighted sample; SE, standard error for weighted sample. ‡ NRT, including any use of nicotine patches, gum, inhaler and lozenges. § Other pharmaceutical aids including bupropion SR and varenicline . ¶ Behavioural support including group counselling, specialized addiction counselling, Ontario Quitline,


or a chat group to help quit smoking.

221

Table 52. Comparison between smokers using gum only ≥8 weeks and using patches only ≥8 weeks (not using other NRT products) among those who made at least one serious quit attempt at follow-up, OTS longitudinal study 2005-2009

Using gum

≥8 weeks only (N=54)

Using patches

≥8 weeks only (N=27)

P value Timing Characteristics % %

Baseline Socio‐demographic characteristics Age (years) Mean (SD)† 49.3 (9.5) 48.7 (12.3) 0.81 Median (min‐max) 49.0 (18‐62) 47.5 (18‐82) 18‐24 0.0 5.6 0.55 25‐39 11.5 11.1 40‐54 53.9 53.7 55‐64 40.0 60.0 65+ 3.9 7.4 Sex Female 63.0 63.0 1.00 Education <High school 3.7 20.4 0.063 High school 25.3 29.6 Some post‐secondary 18.5 11.1 Post‐secondary graduation 51.9 38.9 Marital status Never married 14.8 24.1 0.58 Married/common law 55.6 46.3 Widowed/separated/divorced 29.6 29.6 General health Self‐perceived health Good – Excellent 77.8 79.6 0.85 Poor – Fair 22.2 20.4 Nicotine dependence Smoking status Daily 77.8 90.7 0.17 Occasionally 22.2 9.3 Cigarettes per day Mean (SD)† 15.0 (2.6) 16.9 (8.7) 0.075 Median (min‐max) 13.2 (1.3‐35.7) 15.0 (2.6‐45) 1‐10 cigarettes/day 44.4 18.5 0.13 11‐20 cigarettes/day 29.6 55.6 21+ cigarettes/day 25.9 25.9 Heaviness of smoking index Low 40.9 30.0 0.66 Moderate 36.4 50.0 High 22.7 20.0 Using other tobacco (e.g., cigar,

snus) 3.7 7.4 0.52

222

Past quit history # of lifetime quit attempts Mean (SD)† 4.5 (3.5) 5.2 (5.8) 0.56 Median (min‐max) 3.0 (0‐12) 3.0 (1‐30) Tried to quit in the last 12 months 29.6 35.2 0.62 Planned the most recent quit

attempt 22.2 22.2 1.00 Intention to quit Intention to quit Within the next 30 days 44.4 35.2 0.46 Within 1‐6 months 33.3 35.2 Beyond next 6 months 14.8 18.5 No intention to quit 3.7 5.6 Not applicable 4.6 4.4 A firm date for the planned quit


quitting Self‐perceived addiction Not at all to somewhat addicted 25.9 14.8 0.23 Very addicted 74.1 85.2 Self‐perceived easiness to quit Somewhat to very easy 14.8 7.4 0.30 Somewhat to very hard 85.2 92.6 Self‐perceived confidence to quit

completely Fairly to very confident 66.7 59.3 0.52 Not very to not at all confident 33.3 40.7 Motivational variables for quitting Perceived benefit from quitting Quite a lot to a lot 92.6 94.4 0.75 Not at all to little 7.4 5.6 Main reason for planning to quit To reduce disease risk or improve

health 59.3 46.3 0.27 Social‐environmental factors for


support quitting 81.5 74.1 0.46 Someone making quitting difficult 25.9 57.4 0.0096 Other household member(s)

smoking 3.7 5.6 0.72 No indoor smoking at home 48.2 29.6 0.10 Seeing or hearing an ad about stop

smoking medications such as nicotine patch and gum 81.5 83.3 0.84

223

Quit aids Ever use of quit aid patterns Ever used NRT‡ to quit smoking 88.9 87.0 0.81 Ever used other pharmaceutical

aids§ 40.7 44.4 0.75 Ever used behaviour support¶ 29.6 11.1 0.059 Ever used other quit methods†† 29.3 46.3 0.27 Beliefs about quit medications Using medications making

quitting easier 88.9 87.0 0.81 Difficult to use medications due

to the cost 25.9 40.7 0.23 Hard to get quit medications 3.7 7.4 0.66 Concerning the side effects 25.9 35.2 0.46

Follow‐up

Quit aids at follow‐up Other pharmaceutical aids§ 22.2 20.4 0.85

Behavioural support¶ 22.2 29.6 0.60 Other quit methods†† 37.0 29.6 0.61 Using other tobacco

(e.g., cigar, snus) at FU 11.1 5.6 0.39 # of quit attempts Mean (SD) 2.8 (2.8) 2.9 (5.6) 0.89 Median (min‐max) 1.0 (1‐10) 1.0 (1‐41)

† SD, standard deviation for un‐weighted sample; SE, standard error for weighted sample. ‡ NRT, including any use of nicotine patches, gum, inhaler and lozenges. § Other pharmaceutical aids including bupropion SR and varenicline . ¶ Behavioural support including group counselling, specialized addiction counselling, Ontario Quitline,


or a chat group to help quit smoking.

does duration of nicotine replacement therapy use matter ... · background and objectives: little...

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