Obstructive Sleep Apnea Worsens Diabetes Control

Obstructive sleep apnea (OSA) may worsen diabetes mellitus (DM) control by disrupting the deepest stages of sleep, according to the results of a new study.  

Severe OSA has long been known to lead to poorer glycemic control among patients with type 2 DM. But it is unknown whether obstructive events during rapid eye movement (REM) sleep have a different metabolic impact compared with those during non-REM (NREM) sleep.

“Treatment of OSA is often limited to the first half of the night, when NREM rather than REM sleep predominates,” noted lead author Babak Mokhlesi, MD, Director, Sleep Disorders Center, at the University of Chicago.

Dr Mokhlesi and colleagues aimed to quantify the impact of OSA in REM versus NREM sleep on hemoglobin A_1c (HbA_1c) level in 115 patients with type 2 DM. All the patients, average age 56 years, underwent polysomnography, and glycemic control was assessed by HbA_1c. Their average body mass index of 35 kg/m² placed them in the obese category.

In a multivariate linear regression model, REM apnea–hypopnea index (AHI) was independently associated with increasing levels of HbA_1c. In contrast, NREM AHI was not associated with HbA_1c levels. The mean adjusted HbA_1c level increased from 6.3% in participants in the lowest quartile of REM AHI to 7.3% in those in the highest quartile of REM AHI.

“Our model predicts that 4 hours of CPAP use would leave 60% of REM sleep untreated and would be associated with a decrease in HbA_1c by approximately 0.25%,” the authors stated. “In contrast, 7 hours of CPAP use would cover more than 85% of REM sleep and would be associated with a decrease in HbA_1c by as much as 1%.”

Although most REM sleep occurs in the early morning hours before waking, research shows that many patients remove their CPAP mask in the middle of the night because it can feel uncomfortable, said Dr Mokhlesi. As a result, their sleep apnea is more likely to go untreated during REM sleep, a time that may be particularly important for patients with DM.

The researchers concluded that in type 2 DM, OSA during REM sleep may influence long-term glycemic control. “The metabolic benefits of CPAP therapy may not be achieved with the typical adherence of 4 hours per night,” they stated. 

The findings provide another good reason for those with OSA to wear a CPAP mask that helps ensure uninterrupted breathing, the standard treatment for the condition, throughout the night.

The researchers published their results in the March 1, 2014, issue of Diabetes Care.