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Sleep Disorders and Diabetes
CPAP Therapy in Type 2 Diabetes Patients With OSA Improves Glycemic Control During Sleep
Type 2 diabetes and obstructive sleep apnea (OSA) often occur together. Estimates of the prevalence of OSA among individuals with type 2 diabetes range from 18% to 36%.1-3 It has also been estimated that close to 50% of patients with OSA have type 2 diabetes or impaired carbohydrate metabolism.4 Other research5,6 shows the prevalence of type 2 diabetes in OSA patients to be about 15%. The International Diabetes Federation (IDF) Task Force on Epidemiology and Prevention released a statement saying that research demonstrates that type 2 diabetes and OSA are closely related and that both disorders have significant implications on public health and on individuals7 (Tables 1 and 2).
Obesity is a common factor in both conditions, although OSA has been shown to be associated with increased insulin resistance independent of obesity.8,9
Previous studies have shown inconsistent effects of the treatment of OSA using the gold standard of continuous positive airway pressure (CPAP) on glycemic control.10,11 Babu et al12 found, however, an improvement in postprandial blood glucose in type 2 diabetes patients with OSA after treatment with CPAP for 3 months. Arthur Dawson, MD, from the Scripps Clinic Sleep Center, and colleagues, reported in the Journal of Clinical Sleep Medicine (2008;4:538–542) that endpoints such as A1C and insulin sensitivity might not reflect short-term changes in glycemic control during sleep.
Dr. Dawson and colleagues used a continuous glucose monitoring system to measure glucose levels during polysomnography recordings of sleep among 20 patients with type 2 diabetes who had moderate-to-severe OSA before treatment and then after 4 to 12 weeks of treatment with CPAP. Included patients were on a stable diabetes regimen and were newly diagnosed with OSA with no previous CPAP treatment.
Results showed that in this group of patients—most of whom were obese—sleeping and nocturnal hyperglycemia were reduced, and the sleeping interstitial glucose level was less variable during CPAP treatment. The average glucose level during sleep decreased by approximately 20 mg/dL after an average of 41 days of CPAP, Dr. Dawson and colleagues found. The sleeping glucose level was also more stable after treatment, with the median standard deviation decreasing from 20.0 to 13.0 and the mean difference between maximum and minimum values decreasing from 88 to 57.
In a news release from the American Academy of Sleep Medicine, Dr. Dawson said, "The low blood oxygen level and the arousals associated with an apneic event activate the sympathetic nervous system and cause the release of stress hormones, both of which tend to raise the blood glucose. If we could prevent these apneic events with CPAP, then we might keep the glucose level lower and more stable through the night."
Dr. Dawson said he and his colleagues believe that recognizing and treating OSA could improve outcomes in individuals who have type 2 diabetes and OSA. He added that by using a continuous glucose monitoring system they were able to pick up short-term changes in the glucose level that would not be detected by traditional measurements.
For more on OSA and diabetes, see the supplement that mailed with the February 2009 issue of Review of Endocrinology, available at: www.reviewofendo.com/articles/0209/0209_supp.pdf.
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