Association between Daytime Napping and Incident Arrhythmias: A Prospective Cohort Study and a Mendelian Randomization Analysis

Background Emerging evidence has linked daytime napping with the risk of cardiovascular events. Cardiac arrhythmias are considered as early-stage clinical stage for cardiovascular diseases. However, whether napping frequency is associated with incident arrhythmias remains unknown. Objective This study aims to prospectively investigate the association between napping frequency and cardiac arrhythmias. Methods Daytime napping frequency was self-reported in response to touchscreen questionnaires. The primary outcomes were incident arrhythmias, including atrial fibrillation/flutter (AF/Af), ventricular arrhythmias, and bradyarrhythmia. Cox regression analysis was conducted based on 491,117 participants free of cardiac arrhythmias from UK Biobank (UKB). The two-sample Mendelian randomization (MR) and one-sample MR were used to ensure a causal effect of genetically predicted daytime napping on the risk of arrhythmias. Results During a median follow-up of 11.91 years, 28,801 incident AF/Af, 4,132 incident ventricular arrhythmias, and 11,616 incident bradyarrhythmia were documented. Compared with never/rarely napping, usually napping was significantly associated with higher risks of AF/Af (HR: 1.141; 95% CI: 1.083-1.203)) and bradyarrhythmia (HR: 1.138; 95% CI: 1.049-1.235), but not ventricular arrhythmias, after adjustment for various covariates. The two-sample MR and one-sample MR analysis showed that increased daytime napping frequency was likely to be a potential causal risk factor for AF/Af in FinnGEN (OR, 1.626; 95% CI, 1.061–2.943) and bradyarrhythmia in UKB (OR, 1.005, 95% CI, 1.002–1.008). Conclusions The results of this study add to the burgeoning evidence of an association between daytime napping frequency and an increased risk of cardiac arrhythmias including AF/Af, ventricular arrhythmias, and bradyarrhythmia.