ST. LOUIS — Sleep apnea assessment and treatment should be considered an integral part of diabetes management, Susan M. LaRue, R.D., said at the annual meeting of the American Association of Diabetes Educators.
“Sleep apnea is highly prevalent in people with diabetes, people with hypertension and obesity, all of which we see in huge numbers in our patient population,” said Ms. LaRue, a certified diabetes educator with Amylin Pharmaceuticals.
What's more, data suggest that the majority of obstructive sleep apnea (OSA) cases among people with and without diabetes are undiagnosed, she said.
Because sleep apnea is so common in people with diabetes—concomitant with obesity and hypertension—the Scripps' Whittier Institute for Diabetes, La Jolla, Calif., has instituted a “best practice” in which every patient is screened for OSA, and those found to have the condition are referred for treatment and follow-up.
In a study published by the Whittier's Dr. Daniel Einhorn and his associates, 72.4% of 279 adults with type 2 diabetes were found to have some degree of sleep apnea, defined as an apnea-hypopnea index (AHI) of five events or more per hour. Over a third of the patients (35.8%) had an AHI of at least 15 events per hour, a more severe apnea level associated with a doubling of the risk for the development of hypertension after adjustment for comorbidities such as body mass index (BMI), alcohol use, and cigarette smoking (Endocrine Practice 2007;13:355–62).
The proportion of those with an AHI at or above 15 events per hour was much higher among men than women (49% vs. 21%). Other significant risk factors included age 62 years and older, a BMI of 30 kg/m
That study and the symposium in which Ms. LaRue spoke were both sponsored by the ResMed Corp., which manufactures continuous positive airway pressure (CPAP) devices for treatment of OSA.
Diabetes is among several cardiovascular-related conditions that are strongly associated with OSA. Data suggest that OSA is present in about 80% of individuals with drug-resistant hypertension (35% of all hypertension), in 50% of those with congestive heart failure, and in 50% of those with atrial fibrillation. It is found in 77% of the morbidly obese population.
The mechanism for the association is not known, but theories focus on the increased sympathetic nervous activity resulting from repeated apneas. The resulting higher cortisol levels are related to insulin resistance, which predisposes to impaired glucose tolerance and other cardiovascular risk factors, said Ms. LaRue, formerly with the Whittier Institute.
A study in which the results of overnight polysomnography and oral glucose tolerance testing were compared in 30 obese (but not diabetic) patients with OSA and in 27 equally obese individuals without OSA showed that those who had OSA were more insulin resistant, independent of the degree and distribution of adiposity. The authors hypothesized that the worsening in insulin sensitivity in the OSA patients could reflect the hypoxic state and would account for the increased vascular risk (Clin. Endocrinol. 2003;59:374–9).
Treatment of OSA with CPAP not only reduces apneic episodes and improves sleep quality, but also appears to improve the cardiovascular and metabolic abnormalities. In a German study of 60 patients with moderate to severe OSA, those who were given “therapeutic” levels of CPAP for an average of 9 weeks had a 95% reduction in apneas and hypopneas and a decrease in mean arterial blood pressure of 9.9 mm Hg.
That level of decline would be predicted to reduce coronary heart disease event risk by 37% and stroke risk by 56%, the authors wrote (Circulation 2003;107:68–73).
Insulin sensitivity was significantly improved at 2 days and at 3 months of CPAP therapy among 40 patients with an AHI greater than 20, more so among those with BMIs less than 30 kg/m
Another study of 25 patients with type 2 diabetes and sleep-disordered breathing demonstrated that an average of 83 days' treatment with CPAP significantly reduced postprandial glucose values, by about 60 mg/dL after each meal. Hemoglobin A1c (HbA1c) levels also dropped significantly among those with a baseline level greater than 7% (from 9.2% to 8.6%). Reduction in HbA1c was significantly correlated with days of CPAP use among those who wore the device for more than 4 hours per day (Arch. Intern. Med. 2005;165:447–52).
“When sleep apnea is treated appropriately, look at the benefits. … It's another tool to help patients live [more healthily] with diabetes,” Ms. LaRue noted.