Atrial fibrillation, or AFib as it’s commonly called, is an irregular heartbeat that can lead to blood clots and a higher risk of stroke.
This new science doesn’t mean that any of us should panic and cut back on our training, particularly if our exercise routines are relatively moderate. But it suggests that no one is immune from heart problems, no matter how fit we feel.
Exercise changes hearts, usually for the better
Numerous research shows that physically active people are substantially less likely to develop or die from heart problems than people who exercise infrequently.
Exercise demands a lot of our heart. As soon as we start running or otherwise exercising, our hearts double or triple the rate at which they pump blood to our struggling muscles.
Over time, this effort strengthens our hearts, just as it does other muscles, reshaping the organ, including its atria, which are the heart’s upper chambers. The atria carry blood to the lower chambers, the ventricles, which pump it forward. Overall, these changes are desirable and welcome.
But for reasons that remain mysterious, years of repeated, strenuous training and racing can take a toll on the heart, according to some emerging research.
In a much-discussed 2019 study, for example, Swedish scientists compiled the medical records of 208,654 Swedish finalists in the Vasaloppet, a grueling series of cross-country ski races over distances of up to 90 kilometers (56 miles), and compiled them compared to 527,448 Swedish men and women who did not enter the race.
Swedes tend to be active, but the hearts of some who completed a Vasaloppet showed strain, the researchers found. Overall, the skiers did not show a higher risk of atrial fibrillation than the other Swedes. But those male skiers who entered the most races or finished with the fastest times, suggesting they trained the hardest, were more likely than anyone else, skiers or non-skiers, to develop atrial fibrillation in later years. (Female skiers had the lowest rates of atrial fibrillation of any group in the study.)
The greatest risk comes with the most exercise
Essentially, the study found that highly trained athletes have a higher risk of atrial fibrillation than people who exercise less, although the overall risk remains low, said Kasper Andersen, a physician and epidemiologist at Uppsala University in Sweden. , who oversaw the skier study .
This idea was reinforced in the latest study of athletes and atrial fibrillation, published in April in the Clinical Journal of Sports Medicine, which in 2021 compiled training and medical data from 942 longtime endurance athletes, men and women. All had, at some point, competed locally or nationally and most still race.
About 20% of these athletes, almost all middle-aged men, reported having received a diagnosis of atrial fibrillation. Three percent of them had had a stroke.
As with skiers, athletes who trained the most, in terms of years of competition and hours of training per week, were at the highest risk of atrial fibrillation, particularly if they were men and, more surprisingly, swimmers (including triathletes).
There was a higher rate of atrial fibrillation in the most avid athletes than in the general population, said Susil Pallikadavath, a clinical researcher in cardiology at the University of Leicester in England who led the study. But he wasn’t a random sample and the incidence was likely high, he added, since athletes with atrial fibrillation likely responded in disproportionate numbers. He’s also not sure why swimming increased the risks in his study of him, although the prone position for the sport may contribute. (There is no evidence that covid-19 infections affected outcomes; most athletes with atrial fibrillation were diagnosed well before the pandemic began.)
Pay attention to your heart
What does this research mean for those of us who often train or compete?
First, don’t overreact, said Meagan Wasfy, a sports cardiologist at Mass General Brigham Hospital in Boston who has studied and treated atrial fibrillation in athletes. Moderate exercise, i.e. walking or jogging for a few hours a week, protects us from heart problems of all kinds, including atrial fibrillation but also from coronary artery disease, or plaque in the arteries, the most deadly cardiovascular disease.
By all means, keep exercising, she said.
But, on the other hand, don’t underreact and ignore new symptoms, just because you exercise. Your risk of developing AFib can increase three to five times in your lifetime if you spend many, many hours each week exercising, she said.
So, pay attention to sudden heart palpitations or shortness of breath, she said, especially during exercise. Ditto for unexplained drops in your performance. If you’re wearing a smartwatch with a heart rate monitor, note any spikes in your heart rate.
These precautions apply to women, as well as men, Pallikadavath said. To date, longtime female athletes have shown a little extra risk of atrial fibrillation, but there have been few to study. We really need to explore risk in female athletes, she said.
However, he wants athletes to be reassured. The benefits of exercise far outweigh the risks, she said. This message cannot be stated enough.
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