Older women with high levels of physical activity showed twice the risk of atrial fibrillation (AFib) over 10 years as they did for cardiac disease or stroke, based on data from 46 cross-country skiers.
Although previous research suggests that women derive greater health benefits from endurance sports, compared with men, women are generally underrepresented in sports cardiology research, and most previous studies have focused on younger women, Marius Myrstad, MD, of Baerum Hospital, Gjettum, Norway, said in a presentation at the annual congress of the European Association of Preventive Cardiology.
Previous research also has shown an increased risk of AFib in male endurance athletes, but similar data on women are lacking, Dr. Myrstad said.
The researchers reviewed data from the Birkebeiner Ageing Study, a study of Norwegian cross-country skiers aged 65 years and older who were followed for 10 years. The participants were competitors in the 2009/2010 Birkebeiner race, a 54-km cross country ski race in Norway.
Participants responded to a questionnaire addressing cardiovascular disease risk factors, exercise habits, and other health issues. The mean age at baseline was 67.5 year. A total of 34 participants (76%) were available for follow-up visits in 2014, and 36 attended a follow-up visit in 2020. Cumulative exposure to exercise was 26 years.
A total of 86% of the women reported moderate to vigorous exercise in the past year at baseline; 61% did so at the 2020 follow-up visit. One of the participants died during the study period.
“The baseline prevalence of cardiovascular conditions was very low,” Dr. Myrstad noted.
However, despite a low prevalence of cardiovascular risk factors, the risk of AFib in the study population was twice as high as for other cardiac diseases and stroke (15.6%, 7.1%, and 7.1%, respectively).
The mechanism of action for the increased AFib remains unclear, but the current study highlights the need for large, prospective studies of female athletes to address not only AFib, but also exercise-induced cardiac remodeling and cardiovascular health in general, said Dr. Myrstad.
The findings were limited by the small sample size and use of self-reports, Dr. Myrstad said, and more research is needed to clarify the association between increased AFib and high-level athletic activity in women.
“We should strive to close the gap between female and male athletes in sports cardiology research,” he added.
Consider the big picture of AFib risk
This study is important because of the growing recognition that atrial fibrillation may be a preventable disease, said Gregory Marcus, MD, a cardiologist at the University of California, San Francisco, said in an interview.
American Heart Association
Dr. Gregory M. Marcus
“Various behaviors or exposures that are under the control of the individual patient may reveal especially powerful means to help reduce risk,” he added.
Dr. Marcus said he was not surprised by the current study findings, as they reflect those of other studies suggesting a heightened risk for atrial fibrillation associated with very excessive exercise. However, the study was limited by the relatively small size and lack of a comparison group, he said. In addition, “The study was observational, and therefore the possibility that factors other than the predictor of interest, in this case intensive endurance exercise, were truly causal of atrial fibrillation could not be excluded,” he noted.
“It is very important to place this specialized analysis in the greater context of the full weight of evidence related to physical activity and atrial fibrillation,” said Dr. Marcus. “Specifically, when it comes to the general public and the great majority of patients we see in clinical practice, encouraging more physical activity is generally the best approach to reduce risks of atrial fibrillation,” he said. “It appears to be only in extraordinarily rigorous and prolonged endurance exercise that higher risks of atrial fibrillation may result,” he noted.
However, “Exercise also has many other benefits, related to overall cardiovascular health, brain health, bone health, and even cancer risk reduction, such that, even among the highly trained endurance athletes, the net benefit versus risk remains unknown,” he said.
“While the risk of atrial fibrillation in these highly trained endurance athletes was higher than expected, it still occurred in the minority,” Dr. Marcus said. “Therefore, there are certainly other factors yet to be identified that influence this heightened atrial fibrillation risk, and future research aimed at elucidating these other factors may help identify individuals more or less prone to atrial fibrillation or other behaviors that can help mitigate that risk.”
Dr. Myrstad disclosed lecture fees from Bayer, Boehringer-Ingelheim, Bristol Myers Squibb, MSD, and Pfizer unrelated to the current study. Dr. Marcus disclosed serving as a consultant for Johnson and Johnson and InCarda, and holding equity as a cofounder of InCarda.