Reduced life expectancy due to smoking in large-scale cohort studies in Japan.

BACKGROUND

To show the reduction in life expectancy due to smoking and the recovery of normal life expectancy by smoking cessation is useful for tobacco control health policy.

METHODS

This study included 140,026 males and 156,810 females aged 40-79 years, who were participants of large-scale cohort studies in Japan (Japan Health Center-based Prospective Study [JPHC]-I, JPHC-II, Three-Prefecture Study, and Japan Collaborative Cohort [JACC] Study), which commenced around 1990. The mean follow-up period (+/-standard deviation) was 9.6 +/- 2.3 years, during which 16,282 men and 9,418 women died. For persons aged 40-79 years grouped according to each defined smoking status in the baseline questionnaire, sex- and age-specific death rates at attained ages were calculated. The age-specific death rate was calculated by dividing the number of persons who died at the age by the number of persons who were followed-up at the attained age. From these death rates, current life tables were constructed according to the smoking status, and survival curves were plotted.

RESULTS

The life expectancy of male smokers, ex-smokers, and never-smokers at age 40 years was 38.5, 40.8, and 42.4 years respectively. In women, the corresponding life expectancies were 42.4, 42.1, and 46.1 years. In both sexes, the age by which half of the current smokers had died was approximately 4 years younger than that for never-smokers. The life expectancies of male ex-smokers who quit smoking before ages 40, 50, 60, and 70 years were 4.8, 3.7, 1.6, and 0.5 years longer than those of smokers, respectively.

CONCLUSION

Smoking considerably reduced the life expectancy, and earlier smoking cessation resulted in a better survival than that seen with continued smoking.