Sleep-wake cycle irregularities in type 2 diabetics

BACKGROUND The incidence of type 2 diabetes mellitus (T2DM) has been increasing in recent years. Sleep loss and circadian rhythm abnormalities are thought to be one of the underlying causes of adverse metabolic health. However, little is known about sleep-wake cycle irregularities in T2DM. The present study compared the bedtime, waking time, and estimated sleep duration between T2DM and non-T2DM subjects. METHODS The study subjects were 106 consecutive outpatients with lifestyle-related diseases (males/females = 56/50), who answered a questionnaire on sleep status. Subjects were divided into two groups; non-T2DM (n = 32) and T2DM (n = 74) subjects. RESULTS T2DM subjects retired to bed on weekdays and holidays significantly later than non-T2DM subjects (23:43 versus 22:52, p = 0.0032; 23:45 versus 22:53, p = 0.0038, respectively), and woke up significantly later on weekdays and holidays, compared with non-T2DM subjects (06:39 versus 06:08, p = 0.0325; 06:58 versus 06:24, p = 0.0450, respectively). There was no significant difference in the estimated sleep duration between the two groups. Daytime sleepiness was reported significantly more commonly by T2DM subjects than non-T2DM subjects (p = 0.0195). CONCLUSIONS Sleep-wake cycle irregularities are more common in T2DM subjects than non-T2DM. Confirmation that such irregularity plays a role in the metabolic abnormalities of T2DM requires further investigation in the future. TRIAL REGISTRATION UMIN 000002998.