Background: The purpose of this study was to investigate whether sleep extension lowers blood glucose in patients with type 2 diabetes and chronic sleep restriction, and the moderating role of sleep apnea on the effect of sleep extension.

Methods: This study enrolled 19 adults with type 2 diabetes and a sleep duration of less than 7 hours per night, of whom 16 (84.2 %) had obstructive sleep apnea. They were instructed to sleep at their usual time for 3 weeks as baseline, and then to increase their time in bed by 1 more hour per night for 3 weeks. Their sleep duration was recorded using actigraphy monitoring and sleep logs. Their fasting plasma glucose, glycated albumin, and glycated hemoglobin were measured before and after sleep extension.

Results: Nine of the 19 (47.4 %) participants had a decrease in glycated albumin after sleep extension, and these participants had a significantly higher apnea-hypopnea index (AHI; p < 0.001). The participants with an AHI ≥ 30 times per hour were older (p = 0.04), had a shorter baseline total sleep time measured by actigraphy (p = 0.04), and had a more significant decrease in glycated albumin after sleep extension (p = 0.01). The AHI level was significantly correlated with the extent of decrease in glycated albumin after sleep extension (r = 0.72, p = 0.001).

Conclusion: The current study showed the potential of 3-week sleep extension in decreasing blood glucose in patients with diabetes comorbid with severe obstructive sleep apnea and sleep deprivation.