Abstract Body (Do not enter title and authors here): Background: While physical activity (PA) is associated with a lower risk of atrial fibrillation (AF), prior studies have observed a higher prevalence of AF among athletes. Therefore, we sought to characterize the association between PA and the risk for AF in a large cohort of healthy adults with relatively high levels of self-reported leisure time PA levels.

Methods: Individual participant data from the Cooper Center Longitudinal Study were linked to Medicare administrative claims files. PA volume (MET-min/wk), duration of moderate (< 6 METs), and duration of vigorous PA (≥ 6 METs) PA were measured by self-report at study entry. Other risk factors such as age, current smoking status, weekly alcohol consumption, BMI, blood glucose, systolic blood pressure, and cholesterol were measured using a standard approach. AF was identified using Medicare claims. A proportional hazards illness-death model was used to estimate hazard ratios for incident atrial fibrillation and multivariable-adjusted for all measured baseline covariates.PA was evaluated as an ordinal variable (< 500, 500-1499, 1500-3000, and ≥ 3,000 MET-min/week). In analyses for subtype of activity, moderate and vigorous activity were mutually adjusted and evaluated as a continuous covariate (per hour).

Results: We included 26,549 participants (71.9% men, mean age 54 years at baseline), who received Medicare coverage from 1999 to 2019. After 195,343 person-years of Medicare follow-up time, we observed 3,939 cases of AF. Higher PA was associated with a modest increase in the risk for AF above 1,500 MET-min/week, but with less precision at PA above 3,000 MET-min/week (Figure 1). We also observed vigorous activity, but not moderate activity, was associated with higher risk of AF (Figure 2).

Conclusion: After accounting for covariates, higher PA volume was associated with increased risk of AF at doses more than 3x the guideline-recommended amount. These associations appear to be more apparent for vigorous exercise intensity.