Atrial fibrillation among women in endurance sports: sex-specific risk and mechanisms.

Regular physical activity remains a cornerstone of cardiovascular health; however, prolonged, high-volume endurance training may paradoxically increase the risk of atrial fibrillation (AF). While this association is well established in male population, sex-specific evidence in women is still limited, despite their rapidly growing participation in endurance sport. Epidemiological studies consistently demonstrate a J-shaped association between exercise exposure and AF relative risk in both sexes. Women appear to have a broader protective window, tolerating substantially higher exercise doses (estimated up to ~83 MET-h/week in cohort studies, equivalent to approximately 10-12 h of moderate-to-vigorous endurance training per week) before AF risk begins to rise, whereas men show a risk increase at lower exposure levels. At the extreme end of the spectrum, elite female endurance athletes may also experience elevated AF relative risk, confirming that the upper inflection of the J-curve applies to both sexes. Mechanistic evidence indicate that atrial structural remodelling occurs similarly in men and women, yet sex hormones and autonomic tone appear to modulate arrhythmogenic vulnerability. Overall, current evidence supports sex-aware clinical counselling, promoting the cardiovascular benefits of endurance exercise in women while considering potential risk at very high training loads.