Long sleep duration and afternoon napping are associated with higher risk of incident diabetes in middle-aged and older Chinese: the Dongfeng-Tongji cohort study.

BACKGROUND: In this study, we investigated the independent and combined effects of sleep duration and afternoon napping on the risk of incident diabetes among a cohort of middle-aged and older Chinese adults.

METHODS: Information of sleep and napping was obtained by questionnaires during face-to-face interviews. We categorized sleep duration into <7 h, 7∼<8 h (reference), 8∼<9 h, 9∼<10 h, and ≥ 10 h. Afternoon napping was divided into no napping (0 min) (reference), 1-30 min, 31-60 min, 61-90 min, and > 90 min. Cox proportional hazard regression models were used.

RESULTS: Compared with referential sleeping group, subjects sleeping ≥10 h had a 42% higher risk of developing diabetes. The HR was 1.28 for napping > 90 min when compared with no napping. These associations were more pronounced in individuals without hypertension. Combined effects of long sleep duration and afternoon napping were further identified. Individuals with both sleep duration ≥ 10 h and napping > 60 min had a 72% higher risk of incident diabetes than those with sleeping 7∼<8 h and napping 0 min (all above p < 0.05).

CONCLUSIONS: Both long sleep duration and afternoon napping were independently and jointly associated with higher risk of incident diabetes. Key messages Sleep duration was associated with diabetes, but whether it is a real cause of incident diabetes especially in Chinese still remains to be elucidated. The association of afternoon napping and diabetes was not consistent and definite, we clarified this association in a large prospective study. Long sleep duration and afternoon napping were independently and jointly associated with higher risk of incident diabetes.