Napping Is Associated with Increased Risk of Type 2 Diabetes: The Guangzhou Biobank Cohort Study

Study Objective: Intentional napping is very common, particularly in China. However, there are limited data regarding its potential health effects. We therefore examined the possible relationship between napping and type 2 diabetes. Design: Cross-sectional analysis of baseline data from the Guangzhou Biobank Cohort Study. Setting: Community-based elderly association in Guangzhou, China. Participants: 19,567 Chinese men and women aged 50 years or older. Measurements and Results: Self-reported frequency of napping was obtained by questionnaire and type 2 diabetes was assessed by fasting blood glucose and/or self-reports of physician diagnosis or treatment. Participants reporting frequent naps (4-6 days/week and daily) were 42% to 52% more likely to have diabetes. The relationships remained essentially unchanged after adjustments were made for demographics, lifestyle and sleep habits, health status, adiposity, and metabolic markers (odds ratio for diabetes 1.36 [95% CI 1.17-1.57] in 4-6 days/week, 1.28 [1.15-1.44] in daily nappers). Similar associations were found between napping and impaired fasting glucose. Removal of those with potential ill health and daytime sleepiness did not alter the observed associations. Conclusions: Napping is associated with elevated prevalence of diabetes and impaired fasting glucose in this older Chinese sample. Our finding suggests that it is less likely that diabetes leads to daytime sleepiness. This raises the possibility that napping may increase the risk of diabetes. Confirmation by longitudinal studies is needed.