Xiuqi Qiao,1,2 Xiaoxia Wang,1 Lixin Guo,1,2 Qi Pan1,2 

1Department of Endocrinology, Beijing Hospital, National Center of Gerontology, Institute of Geriatric Medicine, Chinese Academy of Medical Sciences, Beijing, 100730, People’s Republic of China; 2Graduate School of Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing, 100730, People’s Republic of China

Correspondence: Lixin Guo; Qi Pan, Email glx1218@163.com; panqi621@126.com

Background: Prior research based on observations has furnished evidence that supports a connection between daytime napping and the prevalence of non-alcoholic fatty liver disease (NAFLD). Nevertheless, the question of whether this correlation is indicative of a causal link has not been definitively answered.
Methods: We used meta-analysis and Mendelian randomization (MR) to synthesize genetic and observational data. A two-sample MR analysis was conducted, leveraging 105 single-nucleotide polymorphisms (SNPs) known to be associated with daytime napping patterns. Additionally, summary-level data pertaining to NAFLD outcomes were acquired from the comprehensive UK Biobank study. Network meta-analyses were employed to investigate the relationship between excessive daytime napping and NAFLD, while subgroup was also performed.
Results: Significant associations were observed between daytime napping and NAFLD. The systematic review/meta-analysis uncovered a heightened risk of NAFLD development among individuals who engaged in daytime naps exceeding 30 minutes, when compared to those who did not nap(odds ratio [OR] = 1.32, 95% confidence interval [CI]: 1.05 to 1.66). Furthermore, MR analysis indicated that a genetic propensity towards longer daytime napping was significantly linked to an increased likelihood of NAFLD (OR = 2.26, 95% CI: 1.38 to 3.73).
Conclusion: Daytime napping has been found to be causally related to a higher risk of NAFLD. Furthermore, across all participants, napping for an average duration over 30 minutes was linked to an elevated likelihood of NAFLD.

Keywords: daytime napping, non-alcoholic fatty liver disease, genetic variants, Mendelian randomization, network meta-analysis