LAUSR

STUDY OBJECTIVES Previous observational studies have found conflicting evidence on the relationship between daytime napping and incident cardiovascular diseases (CVD), but it remains unclear whether these associations present causality. This study aims to verify whether and why there is a causal relationship between these parameters, and whether there is an aetiological basis. METHODS A two-sample Mendelian randomization analysis was performed using 79 single nucleotide polymorphisms associated with daytime napping. Summary-level data for coronary atherosclerosis, peripheral atherosclerosis, total CVD and five CVD outcomes were obtained from the FinnGen study. Meta-analyses were aimed at investigating the relationships of excessive daytime napping with total CVD, coronary heart disease, myocardial infarction (MI) and stroke incidence. Subgroup, network meta-analysis (NMA) and trial sequential analysis (TSA) were also performed in this study. RESULTS The inverse-variance weighted method demonstrated that a genetic predisposition to more frequent daytime napping was significantly associated with higher odds of coronary atherosclerosis (odds ratio [OR] = 1.55, 95% confidence interval [CI]: 1.11-2.17), MI (OR = 1.63, 95%CI: 1.06-2.50) and heart failure (OR = 1.80, 95%CI: 1.28-2.52). In NMA, an increased risk of developing CVD in people who napped for more than 60 minutes a day than those who did not nap was demonstrated and then supported by TSA results (summary relative risk = 1.98, 95%CI: 1.39-2.82). CONCLUSION Habitual daytime napping is causally associated with an increased risk of incident CVD primarily via the development of coronary atherosclerosis. An average napping duration of more than 60 minutes is associated with an elevated risk of CVD in all participants.