Relation between Metabolic Syndrome and Sleep Duration in Japan: A Large Scale Cross-sectional Study

Objective Previous research suggests that sleep duration is related to metabolic syndrome, based on Western criteria. However, the criteria for metabolic syndrome vary among countries and populations. We therefore evaluated the relationship between sleep duration and the presence of metabolic syndrome in Japan. Methods A cross-sectional study was conducted involving 44,452 apparently healthy individuals aged 20 years or older who underwent annual health checkup the Center for Preventive Medicine at St. Luke's International Hospital in 2008. Participants were divided into 4 groups according to their average reported nightly sleep duration (<6 hours, 6-6.9 hours, 7-7.9 hours, >= 8 hours). Based on criteria by the Japan Society for the Study of Obesity, we identified individuals with metabolic syndrome. Multivariable logistic regression was used to explore the relationship adjusting for age, gender, alcohol consumption, current smoking, past medical history, and level of physical activity. Results The prevalence of metabolic syndrome was 8.7% (3,876/44,452; 95% CI, 8.5-9.0%). The mean age of participants was 44.8 years (SD, 12.8) and 49.5% were male. Those with sleep duration less than 6 hours were more likely to meet metabolic syndrome criteria (OR=1.42; 95% CI=1.20-1.68) than those with longer sleep duration (>= 8 hours). Conclusion Short sleep duration is associated with the presence of metabolic syndrome despite the difference between Japanese and Western criteria.