Association between sleep quality and metabolic syndrome: A systematic review and meta-analysis

•This is the first meta-analysis examining the association between sleep quality and metabolic syndrome using data from epidemiological studies.•Our results indicated that the overall sleep quality as well as sleep complaints have a significant positive association with metabolic syndrome.•These findings support the need for early detection and management of poor sleep quality in the individuals with metabolic syndrome. Sleep quality has been suggested to play an important role in development of metabolic syndrome (MetS). However, the results have been inconsistent. A systematic review of observational studies aimed to evaluate the association between sleep quality and MetS. A comprehensive search was conducted in PubMed and EMBASE. The pooled odd ratios (ORs) were calculated using random effects models. The construction of funnel plot was used to explore publication bias, with further application of Egger's test. 22 studies were included. The pooled finding showed that overall sleep quality had a significant positive association with MetS (OR 1.37, 95% CI 1.15–1.64), with substantial heterogeneity (I2 = 62.4%, P