Smoking and smoking cessation in relation to all-cause mortality and cardiovascular events in 25,464 healthy male Japanese workers

Background: Smoking is still a major health problem among males in Japan. The effects of smoking and quitting on mortality and cardiovascular disease (CVD) need updating. Methods and Results: This was a prospective cohort study with a median follow-up of 7.5 years of a total of 25,464 healthy male Japanese workers aged 20-61 years who were not on any medication. The adjusted hazard ratios (HR; 95% confidence interval) for all-cause death were 1.51 (0.73, 2.94), 1.68 (1.07, 2.70), 1.30 (0.70, 2.34), and those for total CVD events 1.91 (0.72, 4.67), 2.94 (1.65, 5.63), and 3.25 (1.69, 6.54) for light smokers (1-10 cigarettes/day), moderate smokers (11-20/day), and heavy smokers (≥21/day) compared to never-smokers, respectively. Total CVD events increased dose-dependently as the number of cigarettes/day increased. Acute myocardial infarction was increased at any level of smoking. Stroke was increased at a moderate level of smoking. Quitting for ≥4 years, compared with continuing smokers, reduced the HR for all-cause death to 0.64 (0.38, 1.01), and total CVD events to 0.34 (0.17, 0.62). Conclusions: In healthy young- and middle-aged Japanese males, a significant increase in HR for total CVD events was confirmed for a smoking level of 11-20 cigarettes/day. Quitting reduced the HR for total CVD events, with quitting for ≥4 years being statistically significant. A similar trend was observed for all-cause mortality.