While physical activity and exercise protects against cardiovascular disease, athletes have higher risk of atrial fibrillation and other arrhythmias. Graded independent and joint influences of exercise capacity and muscle strength on these diseases are unknown.
All 1.26 million Swedish men who participated in mandatory military conscription between 1972 and 1995 (at a median age of 18.2 years) contributed. Multivariable-adjusted Cox proportional hazards models were used to evaluate the associations of maximal exercise capacity and muscle strength at conscription to subsequent risk of vascular disease and arrhythmias, as identified in national registries.
During a median follow-up of 26.3 years, about 26,000 hospitalizations for vascular disease events and 17,000 for arrhythmias occurred. Exercise capacity was inversely associated with risk of vascular disease (hazard ratio [HR] 0.64; 95% confidence interval [CI] 0.61-0.67]; for 5th vs. 1st quintile) and so was muscle strength (HR 0.79; 0.76-0.83; for 5th vs. 1st quintile ). Similar associations were seen across a range of major vascular disease events. Exercise capacity was associated with incidence of arrhythmias in a U-shaped fashion (HR 0.91; 0.86-0.96; for 3rd vs. 1st quintile, and 0.99; 0.94-1.04; for 5th vs. 1st quintile). Higher muscle strength was associated with lower risk of arrhythmias (HR 0.87; 0.83-0.91; for 5th vs. 1st quintile).
Exercise capacity and muscle strength in late adolescence are independently and jointly associated with long-term risk of vascular disease and arrhythmias. The lower risk of vascular events with higher exercise capacity was not outweighed by higher risk of arrhythmias.