To compare the hazards of cigarette smoking in men who formed their habits at different
periods, and the extent of the reduction in risk when cigarette smoking is stopped
at different ages.
Prospective study that has continued from 1951 to 2001.
United Kingdom.
34 439 male British doctors. Information about their smoking habits was obtained in
1951, and periodically thereafter; cause specific mortality was monitored for 50 years.
Overall mortality by smoking habit, considering separately men born in different periods.
The excess mortality associated with smoking chiefly involved vascular, neoplastic,
and respiratory diseases that can be caused by smoking. Men born in 1900-1930 who
smoked only cigarettes and continued smoking died on average about 10 years younger
than lifelong non-smokers. Cessation at age 60, 50, 40, or 30 years gained, respectively,
about 3, 6, 9, or 10 years of life expectancy. The excess mortality associated with
cigarette smoking was less for men born in the 19th century and was greatest for men
born in the 1920s. The cigarette smoker versus non-smoker probabilities of dying in
middle age (35-69) were 42% nu 24% (a twofold death rate ratio) for those born in
1900-1909, but were 43% nu 15% (a threefold death rate ratio) for those born in the
1920s. At older ages, the cigarette smoker versus non-smoker probabilities of surviving
from age 70 to 90 were 10% nu 12% at the death rates of the 1950s (that is, among
men born around the 1870s) but were 7% nu 33% (again a threefold death rate ratio)
at the death rates of the 1990s (that is, among men born around the 1910s).
A substantial progressive decrease in the mortality rates among non-smokers over the
past half century (due to prevention and improved treatment of disease) has been wholly
outweighed, among cigarette smokers, by a progressive increase in the smoker nu non-smoker
death rate ratio due to earlier and more intensive use of cigarettes. Among the men
born around 1920, prolonged cigarette smoking from early adult life tripled age specific
mortality rates, but cessation at age 50 halved the hazard, and cessation at age 30
avoided almost all of it.