Hazards of smoking and benefits of stopping: UK and worldwide

Richard Peto, University of Oxford

• Many young men started smoking in the first few decades of the 20th century, so full lifelong risks are now known.

• Young women started smoking around mid-century, so hazards in later middle age only just became apparent

Richard Doll: mortality and smoking in male British doctors born 1900-30

34,000 men recruited in 1951 & followed up to 2001

– Moderate hazard for smokers born 1851-1899, as they did not smoke substantial numbers of cigarettes when young

– Bigger hazard for smokers born 1900-1930: about HALF eventually killed by tobacco

– Those who stopped before age 40 (preferably well before 40) avoided nearly all the excess risk in later middle age

THE UK MILLION WOMEN STUDY Valerie Beral, Kirstin Pirie, Richard Peto, unpublished

First large prospective study of women who have smoked throughout adult life

Big risks, even though UK cigarette yields have

been lowered in recent decades

Current vs never-smoker, all-cause mortality ratio*

THE UK MILLION WOMEN STUDY ‘

1.8

2.6

3.4

*Fully standardised mortality ratio, by smoking habit at start of 12-year FU

THE MILLION WOMEN STUDY

All-cause mortality Ex-smokers and current smokers

3.1

2.1

1.7

1.2 1.06

Stopped at age 35-44

Current smokers

Age at starting 18.8 19.0

Cigarettes per day while smoking

14.7 15.3

THE MILLION WOMEN STUDY

THE MILLION WOMEN STUDY

Lung cancer mortality Ex-smokers and current smokers

24.6

13.0

6.4

3.5 1.8 1.5

THE MILLION WOMEN STUDY

All vascular mortality Ex-smokers and current smokers

3.7

2.0

1.8

1.2 1.0

Hospital admission with any mention of

disease/procedure

Current versus never-smoker

Illustration of the effects of a 3-fold difference in annual death rates on mortality at ages 35-79 *

* Taking death rates in smokers to be twice the UK 2009 death rates, and death rates in non-smokers to be two-thirds of these national death rates

78%

47%

Nationwide delay between increase in smoking by young adults

& main increase in tobacco deaths

when they reach middle & old age

eg, USA 1900-2000

Chinese cigarette increase 40 years after US increase

Delayed hazard: observed (1950, 1990) and predicted (2030) proportions of all deaths at ages 35-69 due to tobacco

US (all adults) China (men)

1950 12% 1990 12%

1990 33% 2030 33%

Product of domestic cigarettes in China

0

50

100

150

200

250

1949 1954 1959 1964 1969 1974 1979 1984 1989 1994 1999 2004

Billion

2000 billion

1000 billion

INDIA: 1 million tobacco deaths

per year during the 2010s

Jha et al, NEJM 2008

World tobacco deaths, if current smoking patterns continue

2000-2025 ~150M

2025-2050 ~300M

2050-2100 >500M

TOTAL for the

21st century

~1000M

(1 billion)

Compare with

20th century total

~100M

(0.1 billion)

Prevention of a substantial proportion of the 450 million tobacco deaths before 2050 requires adult cessation

Continuing to reduce the % children starting smoking prevents many deaths,

but its main effect will be on mortality in ~2050 & later

Worldwide, HIV, TOBACCO, ALCOHOL & OBESITY

are the only big causes of death that have increased substantially since 1990 in

some large populations.

Death in old age is inevitable,

but death before old age is not