Critical AnalysisEVA ZIMMERMANFUNDAMENTALS OF EPIDEMIOLOGYTHURSDAY, 10 NOVEMBER 2016

Betel Quid Chewing in Rural Bangladesh: Prevalence, Predictors and Relationship to Blood PressureJulia E Heck,1* Erin L Marcotte,1 Maria Argos,2 Faruque Parvez,3 Alauddin Ahmed,4 Tariqul Islam,4 Golam Sarwar,4 Rabiul Hasan,4 Habibul Ahsan2,3 and Yu Chen5

Critical Questions1.  What gap in knowledge was meant to be filled?• “Few population-based estimates exist on the prevalence and determinants of betel chewing in Bangaldesh”…” previous estimates were not available on use among women.”• Lack of literature on the relation between betel quid chewing and cardiovascular health

2.  What is the hypothesis and aims of the study?• Aim: “The purpose of this investigation was to report the use of betel quid in a large cohort of Bangladeshi men and women and to assess the associations of betel quid with socio-demographic factors, body mass index (BMI) and blood pressure.”• Null Hypothesis (H0): Betel quid chewing is not determined by certain socio-demographic predictors, and is not associated with an increase in body mass index (BMI), nor various deleterious effects on cardiovascular health. • Alternative Hypothesis (HI): Betel quid chewing is determined by certain socio-demographic predictors, and is associated with an increase in body mass index (BMI), along with various deleterious effects on cardiovascular health.

Critical Questions 3.  What were the methods used (including study design, study population, power calculations, sample size determination, approach and techniques)?

• Design: Population-Based Prospective Cohort Study• Study Population: Married men and women, aged 18-75 years at the initial interview, who have lived in the same bari (cluster of homes) for the previous 5 years*Inclusion criteria were chosen to ensure greater stability of residence• Power/Sample Size Calculations: No mention of power or sample size calculations; Final sample size of 19 934 + 95% confidence interval• Approach: After obtaining informed consent, data were collected by standardized in-person interview by trained interviewers. Clinical evaluations were done by local trained physicians.• Appropriate?

4. What are the results?

Critical Questions5.  What are the key conclusions of the study and are they justified?

• Conclusion: • There is considerable burden of betel quid chewing in Bangladesh• Betel quid chewing was associated with older age and lower socioeconomic status• Chewing betel quid without tobacco was related to increases in systolic and diastolic blood pressure and to general and systolic hypertension• Betel quid chewing may be contributing to the burden of vascular diseases in Bangladesh

• Justification: presuming an accurate calculation of the study power, the findings are justified for this particular population in this particular setting

Critical Questions 6.  What are the confounders?

• Confounders adjusted for:  • Baseline age, sex, BMI • Socio-economic factors (educational attainment, occupation, religion, marital status, land ownership)

• Change in weight, use of hypertensive medications, and pack-years of smoking over follow-up period• Reliability of blood pressure measurements (separate reliability study on 61 subjects)• “White coat hypertension”

• Unadjusted Confounders:• Use of hukka or guul (data on these substance was not available for expansion cohort)• Possibility of residual confounding

Critical Questions 7.  What are the limitations of the study and their implications?

• The study was not designed with a focus on betel quid- Quantity chewed- Changes in chewing frequency over time

• Lack of additional health information (cholesterol or physical activity levels)• Lack of information on family history of hypertension • Generalizable?

Critical Questions 8.  What are the study’s strengths and their particular value to the current literature?• Large cohort size; 2000-01 cohort recruited 11 746 individuals, 2006-08 cohort recruited 8 287 individuals • Overall response rate was 97.5%• Follow-up data collected every two years• Reported a population-based estimate on the prevalence and determinants of betel quid chewing• Association of betel quid with cardiovascular health; results were in line with those of other Bangladeshi studies

Critical Questions 9.  What are the public health implications of the findings?

• Betel quid is chewed by 600 million people worldwide; its use is particularly common in Asia and in migrant communities in the West• Betel quid chewing may be contributing to the increasing burden of vascular disease in Bangladesh• Interventions in the study should be designed to address this growing health problem

10.  What is the quality of the discussion, and does it lead to other investigations that expand the field? Discussion is of good quality and suggests:

• There is a generational shift towards lower betel quid use • Are these results generalizable to other populations?