Abstract 15126: Cardiorespiratory Fitness and Atrial Fibrillation: A Population-based Follow-up Study

Abstract

Background: Atrial fibrillation (AF) is the most common arrhythmia worldwide and has a complex association with exercise capacity. The relationship of atrial fibrillation with cardiorespiratory fitness (CRF) has not been previously investigated. Methods: Cardiorespiratory fitness, as assessed by maximal oxygen uptake (VO2max), was measured at baseline in 1,950 middle-aged men (mean 52.6 ± 5.1 years) from the Kuopio Ischaemic Heart Disease Study (KIHD). Results: During an average follow-up of 19.5 years, there were 305 incident AF cases (annual AF rate of 65.1/1000 person-years, 95% CI: 58.2 to 72.8). Overall a non-linear association was observed between CRF and incident atrial fibrillation. Rate of incident AF varied from 11.5 (95% CI: 9.4-14.0) for the first quartile of CRF, to 9.1 (95% CI: 7.4-11.2) for second quartile, 5.7 (95% CI: 4.4-7.4) for third quartile and 6.3 (95% CI: 5.0-8.0) for the fourth quartile respectively, Figure 1. Usual levels of CRF were non-linearly associated with AF risk, Figure 2. Age-adjusted HR comparing top versus bottom fourth of usual CRF levels was 0.67(95% CI: 0.48-0.95), which attenuated to 0.98 (95% CI: 0.66-1.43) upon further adjustment for several risk factors. These findings were comparable across age, body mass index, history of smoking, diabetes and cardiovascular disease status at baseline. Conclusions: Improved fitness as indicated by higher levels of CRF is protective of atrial fibrillation within an optimal range, beyond which the risk of atrial fibrillation rises again. Our findings are congruent with emerging data on the complex relationship between physical fitness and incident AF.