To the Editor In recent years, the potential benefit of endurance sport activity has been questioned because of the potential risk of atrial fibrillation (AF). However, this risk is difficult to quantify, and studies investigating the prevalence of AF in endurance athletes show conflicting results. We read with great interest the article by Boraita et al.1 They retrospectively studied 6813 elite Spanish athletes (35.0% women; mean [SD] age, 22 [7] years) over a long period (1997-2017). They found a very low prevalence of AF (ie, 0.3%).1 Although the results of the study conducted by Boraita et al1 do not provide a conclusive answer to the doubt regarding the association of endurance sport with AF, they provide some important clues. Their results confirm the significant heterogeneity and the methodological limitations of most of the studies on AF in athletes and the subsequent reliability of the derived meta-analyses.