Endurance training increases the risk of atrial fibrillation in women: a matched-cohort study

Abstract

Abstract Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): This work was supported by research grants from Kvinnor och Hälsa and The Swedish Research Council for Sport Science (to Nikola Drca). Objective Previous studies have found that vigorous physical activity, mainly related to endurance sport participation, increases the risk of atrial fibrillation (AF) in men. However, it remains unclear whether vigorous physical activity also influences the risk of AF in women. We aimed to examine whether endurance sport participation may affect AF risk in women. Methods We conducted a matched-cohort study of top Swedish female endurance athletes (n=228 marathon runners, cyclist, and 10 000-meters track runners) active between 1979-1991 and reference individuals (n=1 368) from the general population individually matched by sex, year of birth, and area of living with a 6:1 ratio to the female athletes. The athlete cohort was created by combining all Swedish women who ran the Stockholm Marathon faster than 3.25 hours in any of the races between 1979 and 1991 with all Swedish women competing in the Swedish athletic national championship in 10 000-meter track running and the top-ranked Swedish bicyclist during the same period. Participants were followed up from study entry until AF diagnosis, death, emigration, or December 31, 2017, whichever occurred first. We used the Swedish National Patient Register to determine whether the participants were diagnosed with AF and other covariables. Cox proportional hazards regression models were used for analysis. Results Baseline characteristics are presented in Table 1. Mean age at study entry was 32 (SD ± 8.5) years. During follow-up (mean 28.8 years; SD ± 4.4), 33 cases of AF were diagnosed, including 10 (4.4%) among athletes and 23 (1.7%) among references. Endurance training was associated with an increased AF risk (Figure 1). The hazard ratio for female athletes compared with the reference population was 2.56 (95% confidence interval 1.22 to 5.37) in the univariable model and 3.67 (95% confidence interval 1.71 to 7.87) after adjustment for hypertension. Conclusion High level of endurance sport training is associated with an increased risk of AF in women.