Could marathoners and triathletes have a similar risk of heart disease as couch potatoes? Possibly, according to new research.
A new study published in the journal Mayo Clinic Proceedings found that extreme exercisers were at higher risk of cardiovascular disease. Researchers followed 3,175 participants from 1985–2011 and found those who exercised at least 450 minutes per week — more than three times the recommended federal physical activity guidelines — had a 27% higher risk of developing coronary heart disease at middle age.
Additional research published in the Journal of the American College of Cardiology found 18% of competitive male triathletes exhibited higher risk of developing myocardial fibrosis, scarring of the heart muscle that can lead to congestive heart failure. Those with myocardial scarring had higher blood pressure during exercise and higher left ventricular mass; these were also the participants who’d competed in more middle- and Ironman-distance events than those without myocardial scarring.
“The science is still early but we’re starting to see concerns about cardiovascular abnormalities in endurance athletes,” notes Dr. Vincent Bufalino, a cardiologist and national spokesperson for the American Heart Association. “The research shows that just because you exercise doesn’t mean you’re healthy.”
Although the research didn’t explore why intense exercise was linked to increased risk of heart disease, Dr. Bufalino suspects it might be an overuse injury similar to runners who suffer from knee pain and injuries after years of pounding the pavement.
“The heart has to work excessively to keep up with that level of exercise,” he explains. “The heart muscle thickens to deal with the demand of the increased output.”
It’s also possible that exercising too much releases cortisol, the stress hormone, which increases inflammation that can cause plaque to build up in the arteries, narrowing blood vessels and increasing the risk of a heart attack.
“There is no direct cause and effect. You don’t run a race and develop heart issues,” says Dr. Bufalino. “It takes years, probably decades, to develop.”
POTENTIAL GENDER DIFFERENCES
In both studies, the risks were significantly higher for men. In fact, in the Journal of the American College of Cardiology research, none of the women included in the study developed myocardial fibrosis. Researcher Dr. Gunnar Lund, a cardiologist at University Medical Center Hamburg-Eppendorf in Germany, isn’t certain about the reason for gender differences but suspects hormones could be to blame.
“One explanation would be testosterone, which may have resulted in myocardial damage,” he says. Another explanation would be that males are more ambitious and eager during competition; however, we have no proof for these assumptions.”
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Despite the apparent connections between excess exercise and an increased risk of heart disease, Dr. Bufalino doesn’t advocate canceling your gym membership or burying your sneakers in the back of the closet, noting, “Zero exercise is just as bad as too much.”
Instead, he suggests staying within the recommended federal guidelines of 150 minutes of moderate-intensity physical activity every week and getting regular heart health screenings.
“Exercise has a lot of heart health benefits; it helps control blood pressure, cholesterol, blood sugar and weight,” he says. “We encourage everyone to exercise.”