Atrial Fibrillation in Men Associated With Exercise Intensity Over Time

Young men who undertake endurance exercise for more than 5 hours a week may increase their risk of developing an irregular heart rhythm later in life, according to the results of a new study.

“Physical activity contributes to prevention of several diseases, and in general is good for the well-being of your body and mind. However, frequent high-intensity exercise during many years could increase the risk for atrial fibrillation,” (AF) lead author Dr Nikola Drca, Department of Cardiology, Karolinska Institute, Karolinska Hospital, Stockholm, Sweden, told ConsultantLive. The increase in risk is real, but quite small, he added.

In the Swedish study, the researchers quizzed more than 44,000 men aged 45 to 79 years about their leisure-time physical activity patterns at the ages of 15, 30, 50, and during the past year, when their average age was 60.

They tracked the participants’ heart health for an average of 12 years from 1997 onward to gauge how many developed AF, which is a known risk factor for stroke.

The men who had exercised intensively for more than 5 hours a week were 19% more likely to have developed AF later in their lives than those exercising for less than 1 hour a week. The level of risk rose to 49% among those who did more than 5 hours of exercise a week at the age of 30, but who subsequently did less than an hour by the time they were age 60.

But those who cycled or walked briskly for an hour a day or more at age 60 were about 13% less likely to develop AF than those who did virtually no exercise at all.

Moderation, moderation, moderation

“It seems that moderate doses of physical activity are enough to get the positive effects without acquiring the negative effects, while these benefits are lost with very high intensity and prolonged efforts,” Dr Drca noted.

There are several possible mechanisms by which frequent endurance exercise could increase the risk for AF, he said. These include enlargement of the left atrium, enlargement of and left ventricular hypertrophy, inflammatory changes in the left atrium, and an increase in the activity of the parasympathetic nervous system.

“In our study, the men who had the highest risk of developing atrial fibrillation were those who were very physically active when they were young, but stopped being physical active. I think that moderate intensity regular physical activity that you continue throughout your life is the best way to maximize the benefits obtained by regular exercise while preventing undesirable effects.”

Primary care physicians should “consider all the positive effects of physical activity on several medical conditions and even on extended life expectancy,” said Dr Drca. “Physical inactivity and a sedentary lifestyle is a far bigger problem in the general population than excessive physical activity. However, frequent high-intensity exercise during many years is associated with an increased risk of AF.” This could be an entry into explaining the etiology and pathogenesis of AF to men who exercise vigorously, he said.

The researchers presented their results online in the May 14, 2014, issue of the journal Heart.

Disclosures:

Drca N, Wolk A, Jensen-Urstad, Larsson SC.  Atrial fibrillation is associated with different levels of physical activity levels at different ages in men. Heart. doi: 10.1136/heartjnl-2013-305304.