NEW YORK (Reuters Health) – New research suggests that as the frequency of vigorous exercise increases, so does the risk of atrial fibrillation.

“Although vigorous exercise has numerous health benefits, case reports and limited data suggest that elite athletic men engaging in endurance exercise that increases parasympathetic tone, particularly jogging, may be at higher risk for the development of atrial fibrillation,” Dr. Anthony Aizer, from New York University Langone Medical Center, and colleagues note in the American Journal of Cardiology for June 1.

To explore this topic further, the researchers analyzed data from 16,921 apparently healthy men who participated in the Physicians’ Health Study, a prospective investigation started in 1982.

During follow-up, 1661 men said they developed atrial fibrillation, according to the report.

On questionnaires, vigorous exercise was defined as that which causes the subjects to “break a sweat”. The analysis showed that, relative to no vigorous exercise, vigorous exercise 5 to 7 days per week increased the odds of atrial fibrillation by 20% (p = 0.04).

On subgroup analysis, however, the association was only apparent in men younger than 50 years of age and in joggers. Comparing 5 to 7 days of vigorous exercise with no vigorous exercise, risks for atrial fib were elevated by 74% among younger men and by 53% among joggers.

“As with any observational study, our study cannot prove causality and the present observed associations could be due, at least in part, to residual confounding,” the authors conclude. “However, vigorous exercise was directly associated with severe atrial fibrillation risk factors, and, therefore, it is also possible that more complete control for risk factors would have strengthened the inverse associations observed.”

Reference:
Am J Cardiol 2009;103:1572-1577.