- To evaluate the association between sleep duration and mortality in adults with type 2 diabetes.

- This study was a longitudinal analysis of all-cause mortality according to sleep duration based on the 2007–2015 Korea National Health and Nutrition Examination Survey (KNHANES) linked to the Cause of Death data (ver. 1.1). Adult participants with type 2 diabetes were included in the analysis. According to self-reported sleep duration, participants were divided into five groups (≤ 5 [short sleeper], 6, 7, 8, and ≥ 9 h/day [long sleeper]). All missing values were replaced using multiple imputation. We used Cox proportional hazards models to evaluate the relationship between sleep duration and mortality using age as the time scale.

- Among the final 51,603 participants who were linked to death certificate data, 5,930 (11.5%) had type 2 diabetes. During a median follow-up of 6.5 years, 735 (12.4%) deaths occurred. In multivariable analysis, a J-shaped association between sleep duration and all-cause mortality was observed (P for quadratic trend = 0.003). In particular, long sleep duration was significantly associated with an increased risk of all-cause mortality (adjusted hazard ratio, 1.65; 95% confidence interval, 1.29–2.11. In addition, modifying effects on the relationship between sleep duration and mortality were identified for chronic kidney disease and cancer (P for interaction = 0.003 and 0.002, respectively).

- A J-shaped relationship was identified between sleep duration and all-cause mortality in Korean adults with type 2 diabetes. In particular, a long sleep duration was significantly associated with an increased risk of all-cause mortality.