Smoking and Risk of All-cause Mortality: The Jichi Medical School (JMS) Cohort Study

BACKGROUND: There have been comparatively few large-scale cohort studies analyzing all-cause mortality due to cigarette smoking. The goal of this analysis is to investigate the relationship between smoking status and all-cause mortality, and to evaluate the effect of smoking in the Japanese. METHODS: The baseline data were collected between 1992 and 1995. Ultimately, 10,873 Japanese (4,280 males and 6,593 females) aged 19 years or older from 12 rural communities located across Japan participated in the study. This analysis is based on the results, including the information on those who died and moved out of the communities, obtained by December 31, 2001. The Cox’s proportional hazards model was used to calculate the hazard ratio (HR) of mortality for smoking with adjustment for age, systolic blood pressure, total cholesterol, body mass index, alcohol drinking habit and education. RESULTS: The mean follow-up period was 8.2 years, during which time, 284 males and 192 females died. The multivariate-adjusted HRs for total mortality among former and current smokers compared with never smokers were 1.09 (95% confidence interval [CI]: 0.73-1.61) and 1.65 (95% CI: 1.16-2.35) in males, and 0.98 (95% CI: 0.40-2.42) and 0.91 (95% CI: 0.42-1.95) in females, respectively. Those for the consumption of 1-14, 15-24, and 25+ cigarettes per day among male smokers were 1.62, 1.57, and 1.89, respectively. In females, there was no great difference in all-cause mortality between smokers and never smokers. CONCLUSIONS: The results of our study confirm an increased risk in males of premature death from all causes among Japanese with a smoking habit.