Sleep Duration and Metabolic Syndrome. An Updated Dose–Risk Metaanalysis

RATIONALE: Several studies have reported that both short and long sleep durations are associated with the metabolic syndrome, but whether a dose-response relationship exists is unclear. OBJECTIVES: We performed a metaanalysis to study the magnitude of the association between the different durations of sleep and metabolic syndrome. METHODS: We searched in the databases of PubMed, Web of Science, and Ovid (all Journals@Ovid) from inception to October 4, 2014 for cross-sectional studies where an association between metabolic syndrome and sleep duration was analyzed. MEASUREMENTS AND MAIN RESULTS: Eighteen studies with 75,657 participants were included. Daily sleep duration of 7 to 8 hours was used as the reference group. The odds ratio (OR) of having metabolic syndrome for short (<7 h) sleep was 1.23 (95% CI, 1.11-1.37; P < 0.001; I(2), 71%). The ORs for less than 5 hours, 5 to 6 hours, and 6 to 7 hours of sleep were 1.51 (95% CI, 1.10-2.08; P = 0.01), 1.28 (95% CI, 1.11-1.48; P < 0.001), and 1.16 (95% CI, 1.02-1.31; P = 0.02), respectively. The coefficient of sleep duration on log of ORs was -0.06 ± 0.02 (P = 0.02). The OR for long sleep duration was 1.13 (95% CI, 0.97-1.32; P = 0.10; I(2), 89%). CONCLUSIONS: A dose-response relationship exists between short sleep duration and metabolic syndrome. Those who report a sleep duration of less than 5 hours have a 1.5 higher odds of having metabolic syndrome. Our study does not support the notion that long sleep is associated with metabolic syndrome.