WEDNESDAY, June 12 (HealthDay News) -- Participants in one of the world's most grueling cross-country ski races are at increased risk of developing a heart rhythm disorder (arrhythmia), according to a new study.
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Researchers looked at nearly 53,000 people who completed the 90-kilometer (56-mile) Vasaloppet in Sweden between 1989 and 1998 and were followed until 2005. The Vasaloppet is the world's oldest, longest and largest cross-country skiing race.
The risk of developing an irregular or abnormally fast heart beat (atrial fibrillation) or a too-slow heart beat (bradyarrhythmia) was highest among skiers who completed the most Vasaloppets and had faster finishing times than other contestants, according to the study, published online June 12 in the European Heart Journal.
"We found that those who completed five or more races in a period of 10 years had a 30 percent higher risk of developing any arrhythmia than those who did one race only. Similarly, skiers who had the fastest finishing time relative to the other participants also had a 30 percent higher risk of developing any arrhythmia in subsequent years," Dr. Kasper Andersen, a cardiologist at Uppsala University Hospital in Sweden, said in a journal news release.
He noted that previous research has examined the effects of endurance exercise on cardiovascular problems such as heart disease and stroke. But only a few, smaller studies have investigated its effect on heart rhythm problems, and these studies have tended to look at people who are less active.
"The present study investigates the higher end of the physical activity level scale and shows how very high physical activity level affects risk of arrhythmias," Andersen said. "The skiers in our study are as a group healthier than the general population. We have previously shown that besides higher leisure-time physical activity, the participants in Vasaloppet smoke less, have lower fat and higher fiber consumption, and better physical and mental health than the general population."
The findings suggest a dose-response relationship -- "the more races skiers complete and the faster they go, the greater their risk of subsequently developing arrhythmia," Andersen said. "However, it is important to stress that this study does not show that the exercise causes arrhythmias, only that it is associated with an increased risk," he added.
The racers have about half the death rate compared to the rest of the population, Andersen said. This is probably because of the training level of the participants, and also because they need to be healthy to even consider participating in the race, he added.
-- Robert Preidt
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SOURCE: European Heart Journal, news release, June 11, 2013
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