Risk of arrhythmias in 52 755 long-distance cross-country skiers: a cohort study

Aims We aimed to investigate the association of number of completed races and finishing time with risk of arrhythmias among participants of Vasaloppet, a 90 km cross-country skiing event. Methods and results All the participants without cardiovascular disease who completed Vasaloppet during 1989-98 were followed through national registries until December 2005. Primary outcome was hospitalization for any arrhythmia and secondary outcomes were atrial fibrillation/flutter (AF), bradyarrhythmias, other supraventricular tachycardias (SVT), and ventricular tachycardia/ventricular fibrillation/cardiac arrest (VT/VF/CA). Among 52 755 participants, 919 experienced arrhythmia during follow-up. Adjusting for age, education, and occupational status, those who completed the highest number of races during the period had higher risk of any arrhythmias [hazard ratio (HR) 1.30; 95% CI 1.08-1.58; for >= 5 vs. 1 completed race], AF (HR 1.29; 95% CI 1.04-1.61), and bradyarrhythmias (HR 2.10; 95% CI 1.28-3.47). Those who had the fastest relative finishing time also had higher risk of any arrhythmias (HR 1.30; 95% CI 1.04-1.62; for 100-160% vs. >240% of winning time), AF (1.20; 95% CI 0.93-1.55), and bradyarrhythmias (HR 1.85; 95% CI 0.97-3.54). SVT or VT/VF/CA was not associated with finishing time or number of completed races. Conclusions Among male participants of a 90 km cross-country skiing event, a faster finishing time and a high number of completed races were associated with higher risk of arrhythmias. This was mainly driven by a higher incidence of AF and bradyarrhythmias. No association with SVT or VT/VF/CA was found.