Long-term incidence of pacemaker implantations and bradycardia among cross-country skiers

Bradycardia is more common among well-trained athletes. The associations of training with pacemaker implantations are less known. We aim to investigate the association of endurance training with incidence of bradycardia and pacemaker implantations in a cohort of endurance athletes. Furthermore, we aim to establish potential sex differences of such associations.

Swedish skiers (209,072) that completed 1 or more races in the 30 to 90 km cross-country skiing event Vasaloppet (1989–2011) and a matched sample (n=531,949) of nonskiers were followed until first event of bradycardia or pacemaker implantation. The Swedish National Patient Register of in-patient and specialized outpatient care was used to obtain the date of diagnoses. Cox regression was used to investigate associations of number of completed races and finishing time with incidence of bradycardia and pacemaker implantations.

Male skiers had higher incidence of bradycardia (hazard ratio [HR], 1.14; 95% CI, 0.99–1.30) and pacemaker implantations (HR, 1.14; 95% CI, 1.02–1.28) than male nonskiers. Male skiers completing most races or with the fastest finishing times had the highest incidence. The incidence of bradycardia (HR, 0.96; 95% CI, 0.70–1.30) and pacemaker implantations (HR, 0.97; 95% CI, 0.75–1.25) among female skiers in Vasaloppet was not different to that of female nonskiers. There was a trend that female skiers completing most races or with fastest finishing times had lower incidence.

Male skiers had higher incidence of bradycardia and pacemaker implantations. Female skiers in Vasaloppet had non-different incidence of bradycardia and pacemaker implantations. Men with the highest number of races and fastest finishing times had the highest incidence of pacemaker implantations. This indicates that bradycardia associated with training is not always as benign as previously suggested. The response appears to be different between sexes.

Type of funding sources: Public Institution(s). Main funding source(s): Uppsala UniversityCKF Dalarna