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Richard Peto a Clinical Trial Service Unit and
Epidemiological Studies Unit (CTSU), Radcliffe Infirmary, Oxford OX2
6HE, b Cancer Epidemiology Unit, Radcliffe Infirmary, Oxford
OX2 6HE, c Trent
Institute for Health Services Research, Queen's Medical Centre,
Nottingham NG7 2UH, d Department of Social Medicine, University of Bristol, Bristol BS8 2PR
Correspondence to: S Darby
sarah.darby{at}ctsu.ox.ac.uk
Objective and design:
To relate UK national trends
since 1950 in smoking, in smoking cessation, and in lung cancer to the
contrasting results from two large case-control studies centred around
1950 and 1990.
Setting:
United Kingdom.
Participants:
Hospital patients under 75 years of age
with and without lung cancer in 1950 and 1990, plus, in 1990, a matched sample of the local population: 1465 case-control pairs in the 1950 study, and 982 cases plus 3185 controls in the 1990 study.
Main outcome measures:
Smoking prevalence and lung cancer.
Results:
For men in early middle age in the United Kingdom the prevalence of smoking halved between 1950 and 1990 but the
death rate from lung cancer at ages 35-54 fell even more rapidly,
indicating some reduction in the risk among continuing smokers. In
contrast, women and older men who were still current smokers in 1990 were more likely than those in 1950 to have been persistent cigarette
smokers throughout adult life and so had higher lung cancer rates than
current smokers in 1950. The cumulative risk of death from lung cancer
by age 75 (in the absence of other causes of death) rose from 6% at
1950 rates to 16% at 1990 rates in male cigarette smokers, and from
1% to 10% in female cigarette smokers. Among both men and women in
1990, however, the former smokers had only a fraction of the lung
cancer rate of continuing smokers, and this fraction fell steeply with
time since stopping. By 1990 cessation had almost halved the number of
lung cancers that would have been expected if the former smokers had
continued. For men who stopped at ages 60, 50, 40, and 30 the
cumulative risks of lung cancer by age 75 were 10%, 6%, 3%, and 2%.
Conclusions:
People who stop smoking, even well into
middle age, avoid most of their subsequent risk of lung cancer, and
stopping before middle age avoids more than 90% of the risk
attributable to tobacco. Mortality in the near future and throughout
the first half of the 21st century could be substantially reduced by
current smokers giving up the habit. In contrast, the extent to which young people henceforth become persistent smokers will affect mortality
rates chiefly in the middle or second half of the 21st century.