The review authors noted that despite the established links between sleep disorders and the development and progression of type 2 diabetes, screening for sleep disorders is not currently a standard part of care for diabetes. To highlight the importance of detecting and treating sleep disorders in people with diabetes, they looked at what previous studies have found regarding the prevalence of sleep problems in this population, as well as the effect of sleep disorders on health outcomes including blood glucose control, cardiovascular complications of diabetes, depression, quality of life, and overall death risk. They also looked for studies showing whether treating sleep disorders could change any of these outcomes.
Sleep problems increase risk of type 2 diabetes
The research review found that sleep problems definitively increased the risk of developing type 2 diabetes. People with a typical sleep duration of less than five hours per night were 48% more likely to develop type 2, and those with poor sleep quality were 40% more likely to develop it. Insomnia was linked to only a slight increase in type 2 diabetes risk of 7%, while obstructive sleep apnea was linked to more than double the risk with a 102% increase. Researchers believe that not getting enough high-quality sleep increases the risk of developing type 2 through harmful effects on glucose metabolism and body weight regulation.
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Several sleep disorders were more common in people with type 2 diabetes than in the general population — including insomnia (affecting 39% of those with type 2), obstructive sleep apnea (affecting 55% to 86%), and restless legs syndrome (affecting 8% to 45%). There wasn’t enough data to conclude whether certain other sleep disorders were more common in people with type 2, including circadian rhythm sleep-wake disorders, central disorders of hypersomnolence, or parasomnias.
Several studies showed that health outcomes were worse in people with diabetes who had sleep disorders. Insomnia was linked to a higher average A1C level (a measure of long-term good glucose control) of 0.23%, as well as a 61% higher chance of developing diabetic retinopathy (eye disease) among people with type 2. It was also linked to a 31% higher risk of depressive symptoms and, shockingly, over seven times the risk of death from all causes among people with type 2. Obstructive sleep apnea, on the other hand, was linked to a higher average A1C level of about 1%, along with 2.64 times the risk for diabetic kidney disease and 3.97 times the risk for diabetic neuropathy (nerve damage). Sleep apnea was also linked to 2.37 times the risk of death from cardiovascular causes in people with type 2.
Unfortunately, there wasn’t much data on the effect of treating sleep disorders in people with type 2 on health outcomes. A few drugs have been shown in small studies to potentially improve sleep quality, and the drug class of dopamine agonists — used to treat restless legs syndrome — was shown in one study to lead to an average drop in A1C of 0.29%. The data on whether continuous positive airway pressure (CPAP) treatment for sleep apnea improves glucose control is inconsistent, with one study showing an average A1C drop of 0.4% but other studies showing no reduction. Lifestyle interventions for weight loss were shown in one study to improve sleep apnea outcomes and reduce A1C by an average of 0.7%, while bariatric (weight-loss) surgery for type 2 was found in a review of studies to resolve sleep apnea entirely in 87.9% of people with the condition.
“Evidence suggests that there is a bidirectional relationship between sleep disorders and type 2 diabetes, implying a vicious circle,” the researchers concluded — meaning that each of the two can contribute to the other. “Since treatment of the sleep disorder could prevent diabetes progression, efforts should be made to diagnose and treat sleep disorders in people with type 2 diabetes in order to ultimately improve health and therefore [quality of life].”