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Elite athletes who participate in endurance sports have a higher risk of heart rhythm problems than recreational athletes, a new Swedish study finds. And those who train for long periods also face an increased risk compared with those who train for less time.
"This study shows, that even though physical activity is generally healthy, athletes committed to endurance sports at elite level have higher risk of suffering from a heart rhythm disorder," said study researcher Dr. Kasper Andersen, a cardiologist at Uppsala University in Sweden.
Earlier studies have reported a higher incidence of some heart rhythm disorders (or arrhythmias) among endurance sport athletes, but these studies have been small.
In the new study, Andersen and colleagues examined data from nearly 47,500 athletes who participated in a cross-country skiing race in Sweden between 1989 and 1998. The race, called the Vasaloppet, is 56 miles (90 kilometers) long and takes place in March each year. Participants range from elite skiers to recreational athletes, and their finishing time is closely related to how much they have trained, the researchers said.
The researchers compared each participant's finishing time with the winning time that year, and counted the number of races completed by the participant (a measure of how long they had been training).
Compared with those who had completed the race once, those who had completed it seven or more times had 29 percent higher risk of developing a heart arrhythmia.
Further, elite athletes, who had finished the race within 1.6 times the winning time had a 37 percent higher risk of arrhythmias than recreational athletes , who finished in more than 2.4 times the winning time. This association was stronger among athletes less than 45 years old.
Intense athletic training can change the structure of the heart, and while it's unclear exactly why, scientists are increasingly recognizing that the changes that come from prolonged athletic conditioning can be similar to those of certain heart diseases, according to a 2006 study from researchers at the Minneapolis Heart Institute Foundation.
In the new study, most of the athletes experienced the most common types of arrhythmia, which are a trial fibrillation (fast irregular heart rhythm) and bradyarrhythmias (slow heart rhythm). The researchers did not find any significant increase in the risk of potentially lethal ventricular arrhythmias (fast heart rhythm originating from the large heart chambers).
The researchers emphasized that the study only compared athletes at different levels. And it's important to note, they said, that the study participants were generally healthy, had a higher than average socioeconomic status and lower mortality than the general population, the researchers said.
Future large studies are needed to compare athletes against the normal population.
The study was presented today at the European Society of Cardiology Congress in Paris.
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