Exercise-Induced Cardiac Remodeling and Atrial Fibrillation in Female Endurance Athletes

Prolonged endurance sport practice is associated with exercise-induced cardiac remodeling (EICR) and increased risk of atrial fibrillation (AF). In a recent editorial in JASE, Petek, Hayes and Wasfy summarized available scientific evidence on EICR and AF among Norwegian cross-country skiers. One of the key points of discussion pertained to the underrepresentation of female athletes.1Petek B.J. Hayes D.M. Wasfy M.M. Right Heart resilience and atrial fibrillation risk in long-term endurance athletes.J Am Soc Echocardiogr. 2022; 35: 1269-1272Abstract Full Text Full Text PDF PubMed Scopus (1) Google Scholar We acknowledge the missed opportunity to evaluate EICR in prior studies and fully support the encouragement to reduce the imbalance between female and male participation in future sports cardiology studies. However, we argue that female underrepresentation in studies may reflect, at least in part, bona fide sex differences in exposure and outcomes. Until recently, women have been outnumbered by men in endurance sports, and differences in the female athlete's career endure. Shorter race distances offered to female competitors may result in a lower cumulative exposure to exercise. This is potentially compounded by poorer incentives and opportunities for female athletes to pursue professional careers. The limited evidence available also suggests less pronounced EICR and a low incidence of AF in female athletes.2D'Ascenzi F. Pelliccia A. Solari M. et al.Normative reference values of right Heart in competitive athletes: a systematic review and meta-analysis.J Am Soc Echocardiogr. 2017; 30: 845-858.e2Abstract Full Text Full Text PDF PubMed Scopus (49) Google Scholar This, together with a later average onset of AF in women compared with men, has resulted in a very low number of endpoints in previous studies. In the Birkebeiner Atrial Fibrillation Study, 110 of 1,449 female participants self-reported AF occurrence and exercise duration.3Myrstad M. Aarønæs M. Graff-Iversen S. et al.Does endurance exercise cause atrial fibrillation in women?.Int J Cardiol. 2015; 184: 431-432Abstract Full Text Full Text PDF PubMed Scopus (26) Google Scholar The majority (84%) of AF cases occurred in women without any or only short exposure to endurance sports, suggesting such cases were unlikely exercise induced. Of 310 women with a cumulative exposure to endurance exercise ≥20 years, AF was reported in 18 individuals, but the diagnosis could only be confirmed in 6 of these. Due to conventional scientific principles of statistical power and sufficient sample size, we chose to exclude females from the subsequent cardiac evaluation study addressing exercise-induced AF. However, although not statistically significant, the results from the Birkebeiner Atrial Fibrillation Study suggested an increased risk of AF among females exposed to decades of endurance exercise and emphasizes the need for further investigation.3Myrstad M. Aarønæs M. Graff-Iversen S. et al.Does endurance exercise cause atrial fibrillation in women?.Int J Cardiol. 2015; 184: 431-432Abstract Full Text Full Text PDF PubMed Scopus (26) Google Scholar Promising prospective studies are underway that will expand our understanding of EICR and cardiac arrhythmias in both female and male athletes.4De Bosscher R. Dausin C. Janssens K. et al.Rationale and design of the PROspective ATHletic Heart ([email protected]) study: long-term assessment of the determinants of cardiac remodelling and its clinical consequences in endurance athletes.BMJ Open Sport Exerc Med. 2022; 8: e001309Crossref PubMed Scopus (7) Google Scholar,5https://clinicaltrials.gov/ct2/show/NCT04991337Date accessed: December 6, 2022Google Scholar We must acknowledge the persistent sex differences in endurance sport participation, exposure, and outcomes as real challenges, but this does not negate the importance of striving to achieve equal representation in medical science. With commitment from researchers and implementation of targeted strategies, equal representation is achievable. We propose that researchers should prioritize the recruitment of female athletes with prolonged exercise exposure and make efforts to retain female athletes in prospective studies (Figure 1). While the scientific community endeavors to implement these strategies, it is important to normalize and encourage the publication of even small numbers of female phenotypes and outcomes, as these can enable future meta-analyses. You've got to be in it to win it, and researchers should take responsibility for increasing female representation and reducing the knowledge gap regarding EICR, AF, and other cardiac arrhythmias between female and male athletes.