Physical activity and other risk factors in male twin-pairs discordant for coronary heart disease

Abstract

Background: Twin-pairs discordant for coronary heart disease (CHD) can be used to examine the possible contribution of genetic and other familial factors to the relationship between CHD risk factors, in particular physical inactivity at leisure, and CHD. Methods and results: In 1975 at baseline, 8205 men aged 25–69 years of the Finnish Twin Cohort without overt CHD responded to a questionnaire. The outcome measures were hospitalization for CHD or death from CHD before age 70 between 1977 to 1995 based on reliable nationwide registries. Among all men, the age-adjusted relative risk of CHD was 0.52 (95% confidence interval (CI) 0.39, 0.71) in men participating in conditioning exercise compared to sedentary men, based on their questionnaire responses. The age, and covariate (body-mass index, smoking, hypertension, diabetes) adjusted-relative risk was 0.68 (CI 0.50, 0.92). Among the twin-pairs discordant for CHD during follow-up ( N=311), the odds ratio (OR) of having CHD was 0.54 (CI 0.27, 1.09) for conditioning exercisers compared to sedentary men. The point estimates from discordant pairs analyses were of the same magnitude as obtained from the analyses of individuals, though statistically not significant due to smaller samples. In contrast, smoking (OR 3.21) and diabetes (OR 10.0) at baseline were also significant predictors of CHD. Conclusions: By studying twins we were able to examine genetic and other familial selection bias and found further supporting evidence that leisure conditioning physical exercise compared to sedentariness helps prevent CHD in men, but smoking was a stronger risk factor.