NEW ORLEANS — Male physicians who were frequent joggers were found to be at increased risk for atrial fibrillation in a new analysis from the Physicians' Health Study.
The association between frequent vigorous exercise and the development of atrial fibrillation seemed to be limited to running. It didn't extend to men whose main exercise was bicycling, racquet sports, or swimming, Anthony Aizer, M.D., said at the annual scientific sessions of the American Heart Association.
Dr. Aizer added that the study demonstrates an epidemiologic association between frequent jogging and atrial fibrillation (AF), not a cause and effect relationship. “These data in isolation should in no way be interpreted as saying you should change your exercise habits,” he stressed. “Importantly, the observed elevation in risk is offset to some degree by the known benefits of exercise on other atrial fibrillation risk factors.”
Vigorous exercisers in the Physicians' Health Study had lower rates of hypertension, diabetes, cardiovascular disease, and heart failure—all known risk factors for AF. It was only after differences in the prevalence of these risk factors were controlled for that a significant independent association emerged between frequent jogging and AF, said Dr. Aizer of Brigham and Women's Hospital, Boston.
He reported on 15,255 male physicians aged 40-84 with no history of AF at the time they enrolled in the Physicians' Health Study. During 14 years of follow-up, 1,285 of them developed AF. Participants' exercise histories showed that the increased exercise-related risk of AF was largely confined to men who worked out five to seven times per week and within that group, to the joggers. Indeed, men who jogged five to seven times per week had an adjusted 67% increased risk of developing AF, compared with nonexercisers.
Some prior studies that failed to find a link between vigorous exercise and the development of AF did not control for the lower level of other cardiovascular risk factors among frequent exercisers.
If a direct causal link does exist between vigorous exercise and AF, one possibility is that the link is mediated by autonomic nervous system activity (ANS). Exercise modulates ANS, and ANS plays a role in arrhythmias. Yet it's also entirely possible the study findings are due to a detection bias on the part of physicians finely attuned to the signs of arrhythmia, he said.