Context: Physical activity and fitness are believed to reduce premature mortality, but whether genetic factors modify this effect is not known.
Objective: To investigate leisure physical activity and mortality with respect to familial aggregation of health habits during childhood and factors that may enable some individuals to achieve higher levels of fitness.
Design: Prospective twin cohort study.
Subjects: In 1975, at baseline, 7925 healthy men and 7977 healthy women of the Finnish Twin Cohort aged 25 to 64 years who responded to a questionnaire on physical activity habits and known predictors of mortality. Those who reported exercising at least 6 times per month with an intensity corresponding to at least vigorous walking for a mean duration of 30 minutes were classified as conditioning exercisers, those who reported no leisure physical activity were classified as sedentary, and other subjects were classified as occasional exercisers.
Main outcome measures: All-cause mortality and discordant deaths among same-sex twin pairs from 1977 through 1994.
Results: Among the entire cohort, 1253 subjects died. The hazard ratio for death adjusted for age and sex was 0.71 (95% confidence interval [CI], 0.62-0.81) in occasional exercisers and 0.57 (95% CI, 0.45-0.74) in conditioning exercisers, compared with those who were sedentary (Pfor trend <.001). Among the twin pairs who were healthy at baseline and discordant for death (n=434), the odds ratio for death was 0.66 (95% CI, 0.46-0.94) in occasional exercisers and 0.44 (95% CI, 0.23-0.83) in conditioning exercisers compared with those who were sedentary (P for trend, .005). The beneficial effect of physical activity remained after controlling for other predictors of mortality.
Conclusion: Leisure-time physical activity is associated with reduced mortality, even after genetic and other familial factors are taken into account.