Longer habitual afternoon napping is associated with a higher risk for impaired fasting plasma glucose and diabetes mellitus in older adults: results from the Dongfeng-Tongji cohort of retired workers

OBJECTIVES: Afternoon napping is a common habit in China. We used data obtained from the Dongfeng-Tongji cohort to examine if duration of habitual afternoon napping was associated with risks for impaired fasting plasma glucose (IFG) and diabetes mellitus (DM) in a Chinese elderly population. METHODS: A total of 27,009 participants underwent a physical examination, laboratory tests, and face-to-face interview. They were categorized into four groups according to nap duration (no napping, <30, 30 to <60, 60 to <90, and > or =90 min). Logistic regression models were used to examine the odds ratios (ORs) of napping duration with IFG and DM. RESULTS: Of the participants, 18,515 (68.6%) reported regularly taking afternoon naps. Those with longer nap duration had considerably higher prevalence of IFG and DM. Napping duration was associated in a dose-dependent manner with IFG and DM (P<.001). After adjusting for possible confounders, longer nap duration (>60 min; all P<.05) was still significantly associated with increased risk for IFG, and longer nap duration (>30 min) was associated with increased risk for DM; however, this finding was not significant in the group with a nap duration of 60-90 min. CONCLUSIONS: Longer habitual afternoon napping was associated with a moderate increase for DM risk, independent of several covariates. This finding suggests that longer nap duration may represent a novel risk factor for DM and higher blood glucose levels.