Obesity, Fitness and the Risk of Incident Atrial Fibrillation in Healthy Adults

Background: Data on the association between cardiorespiratory fitness and new-onset atrial fibrillation among middle-age adults is limited. The aim of this analysis was to investigate the association between fitness, obesity and new-onset atrial fibrillation among apparently healthy adults.

Methods: We investigated 20,245 self-referred men and women who were annually screened in a tertiary medical center. All subjects were free of atrial fibrillation and had completed maximal exercise stress test according to the Bruce protocol at their baseline visit. Fitness was categorized into age- and sex-specific quintiles (Q) according to Bruce protocol treadmill time. Subjects were categorized at baseline into 2 groups: low fitness (Q1-Q2) and high fitness (Q3-5). The primary end-point was new-onset AF during follow-up.

Results: Mean age of study patients was 48 ± 10 years, and 72% were men. A total of 302 (1.5%) events occurred during an average follow-up of 7.5 ± 5 years. Multivariable Cox regression analysis with adjustment for body mass index showed that low fitness and obesity were both independently associated with increased AF risk (hazard ratio 1.30 [P =0.03] and 1.76 [P<0.0001] respectively). Subgroup analysis showed that fitness-related AF risk was obesity-dependent, such that in the obese group (>= 30 kg/m2) low fitness group showed a significantly higher AF event rate compared with high fitness group (Figure: right panel) whereas among non-obese subjects the rate of events was similar between both fitness groups (Figure: left panel; p for interaction = 0.02).

Conclusions: Our findings suggest that low cardiorespiratory fitness is associated with increased AF risk. This is especially true among obese, apparently healthy adults.