Smoking, smoking cessation, and lung cancer in the UK since 1950: combination of national statistics with two case-control studies

Abstract

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.

Figures

Figure 1

Trends in prevalence of smoking at ages 35-59 (left) and ⩾60 (right) in men and women in the United Kingdom, 1950-98. Prevalences at ages 25-34 were 80% for men and 53% for women in 1948-52 and 39% for men and 33% for women in 1998. Further details are given on the BMJ's website (table A)

Figure 2

Trends in mortality from lung cancer in men and women in the United Kingdom, 1950-97: annual mortality per 105 at ages 35-54 (left) and 55-74 (right) years. Rate in each 20 year age range is mean of rates in the four component five year age groups. Age specific rates from 1950-2 to 1993-7 are given on BMJ's website (tables B and C); at ages 35-54 and 55-74 in 1998 the rates were 17 and 243 (men) and 12 and 20 (women)

Figure 3

Effects of stopping smoking at various ages on the cumulative risk (%) of death from lung cancer up to age 75, at death rates for men in United Kingdom in 1990. (Non-smoker risks are taken from a US prospective study of mortality14)