Cigarette smoking and mortality risk - Twenty-five-year follow-up of the seven countries study

Background: Although most observations in the Seven Countries Study suggest that cigarette smoking is harmful for health, universality of this conclus ion remains controversial. Subjects and Methods: Cohort-specific and pooled smoking habits at baseline (1957-1964) in 12763 men aged 40 through 59 years living in Europe, the Un ited States, and Japan in relation to 25-year mortality followup. Pooled ha zard ratios for smokers vs never smokers were calculated by the Cox proport ional hazards model, adjusting for baseline country of residence, age, body mass index, serum cholesterol, systolic blood pressure, and clinical cardi ovascular disease. Results: Adjusted hazard ratios for all-causes death in smokers compared wi th never smokers were 1.3 (95% confidence interval, 1.2-1.4) for smokers of less than 10 cigarettes per day and 1.8 (95% confidence interval, 1.7-1.9) for smokers of 10 cigarettes per day or more. Hazard ratios were elevated for death due to coronary heart disease, all stroke, other arterial disease , lung cancer, other cancer, chronic obstructive pulmonary disease, and oth er disease in smokers compared with never smokers. Within country, a few in stances in which never smokers had a higher cause-specific death rate than smokers of 10 cigarettes per day or more were attributable to random variat ion associated with low prevalence of never smokers and multiple comparison s. Conclusions: These findings confirm the association of cigarette smoking wi th elevated risk of mortality from all causes, several cardiovascular disea ses, cancer, and chronic obstructive pulmonary disease. Risk associated wit h cigarette smoking is independent of culture.