Newman et al. 2021, Atrial fibrillation in athletes meta-analysis

Systematic review and meta-analysis (British Journal of Sports Medicine). Athletes had about 2.5 times the odds of atrial fibrillation versus non-athlete controls (pooled OR 2.46, 95% CI 1.73-3.51). Endurance and high lifetime training volume raise risk; accumulated lifetime endurance hours (a commonly cited threshold near 2,000 h) is a key predictor. The absolute risk in an individual recreational runner remains low. Moderate.