SLEEP AND DIABETES

Insufficient sleep, either poor quality, timing, or duration, are known to negatively affect blood glucose metabolism. Therefore, it should come as no surprise that the amount of time spent sleeping as well as the quality of sleep are associated with the risk of developing type 2 diabetes and also diabetes management in people with existing diabetes.

Sleep and risk of type 2 diabetes

A recent systematic review and meta-analysis of observational studies has found a U-shaped relationship between sleep duration and the risk of developing type 2 diabetes: either too much or too little sleep is associated with increased risk.

The researchers identified 53 studies including 1,478,297 participants that investigated the effects of sleeping duration, quality and time of day on the risk of developing type 2 diabetes. With respect to duration of sleep, people who slept less than 7 hours per night had an 18% increase in risk of developing diabetes whereas those who slept more than 8 hours had a 13% increase in risk, with 7-8 hours per night associated with the lowest risk overall. Poor sleep quality was perhaps unsurprisingly associated with greater risk than sleep duration, with a 50% increased risk of developing type 2 diabetes in poor sleepers. Finally, people who had a daytime nap of greater than 1 hour duration were found to have a 38% increase in risk of diabetes compared to non-nappers.

Sleep and diabetes management

In general, sleep studies have found that restricting sleep to 4-5 hours per night lowers glucose tolerance and decreases insulin sensitivity in adults.

Type 2 diabetes

Similar to research on the risk of developing type 2 diabetes, a recent systematic review and meta-analysis found a U-shaped relationship between sleep duration and increased glycated haemoglobin (HbA1c). Either too much or too little sleep is associated with increased HbA1c (3-month average blood glucose level).

The researchers identified 20 studies including 69,329 participants that investigated the effects of sleeping duration or quality on glycemic management in people with type 2 diabetes. With respect to duration of sleep, people who slept less than 6 hours per night had higher HbA1c and fasting blood glucose levels, whereas those who slept more than 8 hours had higher HbA1c and fasting blood glucose levels, compared to those sleeping 6-8 hours per night. Poor sleep quality was also associated with higher HbA1c.

Type 1 diabetes

In people with type 1 diabetes, a recent systematic review and meta-analysis of 22 observational studies including 972 children and adults investigated the effects of sleeping duration or quality on glycemic management. In adults, those who slept more than 6 hours per night had significantly lower HbA1c (-0.24%) compared to those sleeping less than 6 hours per night and those who self-reported good sleep quality had significantly lower HbA1c levels (-0.19%). No consistent pattern was seen in children, possibly due to their more variable sleeping patterns.

Non-pharmacological sleep interventions can improve diabetes management

A recent systematic review and meta-analysis found that cognitive behavioural therapy for insomnia and/or sleep hygiene education leads to a significant reduction in glycaemic control in people with insufficient sleep. In people with type 2 diabetes the HbA1c level was 0.43% points lower, a clinically meaningful reduction.

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