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

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.

We performed a metaanalysis to study the magnitude of the association between the different durations of sleep and metabolic syndrome.

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.

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%).

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.