Potential effect of replacing sedentary behavior with physical activity on the risk of atrial fibrillation: results from the UK Biobank and REGARDS study

Background Sedentary behavior (SB) has been associated with cardiovascular disease risk, independent of physical activity (PA) and sleep. However, the effect of replacing SB with PA or sleep on atrial fibrillation (AF) risk remains unclear. Methods We studied 86,096 participants from the United Kingdom Biobank (UKB) and 5,777 from the United States (US) REasons for Geographic And Racial Differences in Stroke (REGARDS) prospective cohort studies who were free of AF at baseline and had valid accelerometry data. The two cohorts were included to evaluate the consistency of associations across distinct populations in the UK and the US, two regions with a high burden of AF. Daily time spent in light PA (LPA), moderate to vigorous PA (MVPA), and SB were derived from accelerometer recordings; sleep was accelerometer-derived in UKB and self-reported in REGARDS. Incident AF was identified using ICD-10 codes (I48.x) listed as either a primary diagnosis, secondary diagnosis, or cause of death through hospital and death registry data linkage in UKB and in a follow-up visit through electrocardiogram and self-reported medical history in REGARDS. Isotemporal substitution models were used to examine replacing 30 minutes of SB with LPA or MVPA in both cohorts and with sleep in UKB on the outcome of incident AF. Results Among the UKB participants [57% female, mean age 56.0 (SD 7.8) years, 98% White race], 4,035 AF cases were identified during a median of 7.9 years of follow-up. Replacing 30 minutes of SB with PA was associated with a slightly lower risk of AF in the minimally adjusted models but the associations were attenuated after full adjustment (LPA: HR 0.99, 95% CI 0.95-1.02; MVPA: HR 1.00, 95% CI 0.99-1.02). The REGARDS participants had an average age of 63 (SD 8.3) years, 55% female, 31% Black and 69% White adults, with 486 AF cases identified. Fully adjusted substitution of 30 minutes of SB with MVPA was associated with lower AF odds (OR 0.80, 95% CI 0.63-1.01), whereas LPA showed no association. In UKB, replacing SB with sleep was not associated with AF risk. The magnitude of the association of MVPA substitution with AF appeared stronger among REGARDS participants aged [&ge;]65 years and those reporting <7 hours/day of sleep. Conclusion Replacing SB with moderate or higher intensity PA may decrease AF risk. In REGARDS, these substitutions appeared to benefit older individuals and those reporting shorter sleep duration. These findings highlight the potential benefit of reducing sedentarism to lower AF burden, warranting validation in future studies.