Day napping and metabolic-associated fatty liver disease: A systematic review and meta-analysis of observational studies

Background: Napping inevitably affects human health, and the association between napping and metabolism-related diseases is being more seriously considered. However, the conclusions of studies on the relationship between napping and fatty liver disease (NAFLD)/metabolic-associated fatty liver disease (MAFLD) remain controversial. Methods: We performed a systematical search to identify eligible studies up to July 31, 2024. The fixed effects model was used to calculate the pooled odds ratio (OR). Subgroup were performed. Sensitivity analyses and meta-regression analysis were carried to explore the heterogeneity. Publication bias was assessed by funnel plot and Egger’s test. Results: 48,248 participants from 13 studies were included in this meta-analysis. The pooled analysis found napping to have an association between the incidence of NAFLD/MAFLD (OR, 1.13; 95% confidence interval (CI), 1.08–1.19; P < .001). The robustness of this study was confirmed using a sensitivity analysis. No apparent heterogeneity or publication bias was observed. Further meta-analysis revealed that short nap duration did not greatly affect the incidence of the disease (OR, 1.01; 95% CI, 0.91–1.12; P = .80). However, long nap duration was significantly linked to high risk of the disease (OR, 1.21; 95% CI, 1.02–1.44; P = .03). Conclusion: Patients with NAFLD/MAFLD may had higher prevalence of napping habit. Future research is warranted to conduct a dose-response analysis, measure the effects of confounding factors, and explore the causal relationships between NAFLD/MAFLD. The research protocol was registered and approved in PROSPERO (registration no: CRD42023439507).