Abstract
BACKGROUND: Physical activity (PA) has previously been suggested to attenuate the risk of atrial fibrillation (AF) conferred by excess body weight and weight gain. We prospectively examined the relationship between body size, weight change, and level of PA in a biracial cohort of middle-aged men and women. METHODS AND RESULTS: Baseline characteristics on risk factor levels were obtained on 14 219 participants from the Atherosclerosis Risk in Communities Study. AF incidence was ascertained from 1987 to 2009. Adjusted Cox proportional hazards models were used to estimate the associations between body mass index, waist circumference, relative weight change, and PA level with incident AF. During follow-up, there were 1775 cases of incident AF. Body mass index and waist circumference were positively associated with AF as was weight loss/gain of >5% initial body weight. An ideal level of PA had a small protective effect on AF risk and partially attenuated the risk of AF associated with excess weight in men but not women: compared with men with a normal body mass index, the risk of AF in obese men with an ideal, intermediate, and poor level of PA at baseline was increased by 37%, 129%, and 156% (Pinteraction=0.04). During follow-up, PA did not modify the association between weight gain and risk of AF. CONCLUSIONS: Obesity and extreme weight change are risk factors for incident AF, whereas being physically active is associated with a small reduction in risk. In men only, being physically active offset some, but not all, of the risk incurred with excess body weight.