Background: The vast scientific literature on smoking and health contains few large studies with direct estimates of long-term mortality by smoking habits. Data have been lacking, particularly for women.
Objective: To study smoking and deaths and causes of death in women and men of middle age (40 to 70 years of age).
Design: Population-based cohort study.
Setting: Norway (the Norwegian Counties Study).
Participants: 24,505 women and 25,034 men who were born between 1925 and 1941.
Measurements: Initial information on smoking habits was collected between 1974 and 1978. Smoking status was also assessed about 5 years and 10 years after the first examination. Death during 1974 to 2000 was studied by using death certificate information.
Results: During follow-up, 2333 women and 4680 men died in middle age. Among women and men, 9% and 14% of never smokers, respectively, and 26% and 41% of continuing heavy smokers (> or =20 cigarettes per day), respectively, died in middle age. Years of life lost among heavy smokers between 40 and 70 years of age were 1.4 years in women and 2.7 years in men, compared with never smokers. Rates of smoking-associated lung cancer were similar in women and men, while lower cardiovascular mortality rates in women explained most of the difference in smoking-associated all-cause mortality between men and women.
Limitations: Data on changes in smoking habits after the baseline examination were not available for all participants and for the last 15 years of follow-up. Mortality levels in middle age may not apply to non-Norwegian populations.
Conclusions: Continuing smoking strongly increased and smoking cessation decreased the risk for death between 40 and 70 years of age for both women and men. Despite similar rates for lung cancer death, women who smoked had lower mortality rates in middle age than men with similar smoking histories due to fewer cardiovascular deaths in women.