High fitness might be associated with the development of new‐onset atrial fibrillation in obese non‐athletic adults

Background Data on the association between AF and fitness are conflicting. Objectives The aim of this analysis was to investigate the association between fitness, obesity and incidence of atrial fibrillation (AF) among apparently healthy non‐athlete adults. Methods We investigated 20 410 self‐referred subjects who were annually screened in a tertiary medical centre. All subjects were free of AF and completed maximal exercise stress test according to the Bruce protocol at baseline. Fitness was categorised into age‐ and sex‐specific quintiles (Q) according to the treadmill time. Subjects were categorised to low (Q1‐Q2) and high fitness (Q3‐5) groups. The primary end point was new‐onset AF during follow‐up. Results Mean age was 48 ± 10 years and 72% were men. A total of 463 (2.3%) events occurred during an average follow‐up of 8 ± 5 years corresponding to an AF event rate of 0.3% per person year. Univariate and multivariate models showed that AF risk was similar in both fitness groups. However, AF event rate was 0.55% per person year among high fitness obese subjects, compared with 0.31% for low fitness obese subjects (P