Objective Since smoking and exercise have opposite effects on coronary risk factors, we hypothesized that smoking may weaken the protective effect of exercise on prevention of coronary heart disease. We aimed to determine the effect of smoking on the relationship between sports participation and mortality from coronary heart disease.
Design Population-based prospective cohort study in Japan. Participants. A total of 76,832 Japanese men and women, aged 40 to 79 years with no history of stroke, coronary heart disease, or cancer, completed a self-administered questionnaire between 1988 and 1990.
Main outcome measures Systematic mortality surveillance was performed through 2003, and 638 coronary heart disease deaths (496 myocardial infarction) were identified.
Results Persons who reported the longest time in sports participation (≥5 hours/week) had approximately 50 to 80% lower age-adjusted risk of mortality from coronary heart disease, compared with those in the second lowest category (1-2 hours/week) among never and ex-smokers, but no association was found among current smokers. Adjustment for known risk factors and exclusion of individuals who died within 2 years of baseline inquiry did not substantially alter these associations. The multivariable hazard ratios (95% confidence interval) of coronary heart disease for the ≥5 hours/week versus 1-2 hours/week of sports participation were 0.44 (0.23 to 0.86) among never smokers, 0.18 (0.05 to 0.60) among ex-smokers, and 0.82 (0.47 to 1.40) among current smokers. These associations were similarly observed between men and women.
Conclusions Smoking could reduce the beneficial effect of sports participation for reduction of fatal coronary heart disease.
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