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Vigorous exercise linked to atrial fibrillation

IHN logoHELSINKI, FINLAND. There is ample evidence that regular physical exercise reduces the risk of cardiovascular disease. It is therefore somewhat surprising that researchers at the Central Military Hospital and the University of Helsinki have found that men who engage in long term vigorous exercise have a five times greater risk of developing lone atrial fibrillation than do less active men. The researchers studied 300 top ranked orienteers aged 35 to 59 years and compared their incidence of atrial fibrillation to the incidence of among 495 healthy controls of the same age group. The orienteers, as expected, had lower overall mortality (1.7 per cent) than controls (8.5 per cent), fewer cases of coronary heart disease since 1985 (2.7 per cent vs. 7.5 per cent), and fewer risk factors for atrial fibrillation. Nevertheless, lone atrial fibrillation was diagnosed in 12 out of 228 orienteers as compared to two out of 212 controls. As a matter of fact, it was later determined that the two controls with atrial fibrillation also were regular participants in vigorous exercise. The first attack of lone atrial fibrillation in the orienteers was at a mean age of 52 years. The researchers conclude that vigorous long term exercise is associated with an increased risk for atrial fibrillation despite its protective effects against heart disease and premature death. They speculate that enhanced vagal tone and atrial enlargement so often found in endurance athletes may predispose to atrial fibrillation. It is not known whether stopping exercise will prevent recurrence of atrial fibrillation.
Karjalainen, Jouko, et al. Lone atrial fibrillation in vigorously exercising middle aged men: case-control study. British Medical Journal, Vol. 316, June 13, 1998, pp. 1784-85

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