Association between habitual daytime napping and metabolic syndrome: a population-based study

Objective: Our objective was to evaluate the association between habitual daytime napping and the prevalence of metabolic syndrome.

Materials and methods: We conducted a population-based study of 8,547 subjects aged 40 years or older. Metabolic syndrome was defined according to a harmonized definition from a joint statement and the recommended thresholds for the Chinese population. Information about sleep duration was self-reported.

Results: The prevalence of metabolic syndrome in the no daytime napping group, the 0 to 1 hour daytime napping group and the more than 1 hour daytime napping group were 35.0%, 36.0% and 44.5% among the females (P<0.0001). Increased daytime napping hours were positively associated with parameters of metabolic syndrome in the female subjects, including waist circumference, systolic blood pressure, triglycerides and fasting plasma glucose (P<0.05 for all). Multivariate adjusted logistic regression analysis revealed that, compared to the no habitual daytime napping females, napping for more than 1 hour was independently associated with an increased prevalence of metabolic syndrome (odds ratio 1.39, 95% confidence interval, 1.13-1.72). Compared to the female subjects in the no daytime napping group, those habitually napped for more than 1 hour exhibited 46% and 26% increases in the prevalence of central obesity and hypertriglyceridemia (all P<0.05). No statistically significant associations were detected between daytime napping hours and metabolic syndrome among the male subjects.

Conclusion: Daytime napping is associated with an increased prevalence of metabolic syndrome in middle-aged non-obese Chinese women.