Screening Diabetes Patients for Obstructive Sleep Apnea

 It has long been known that lack of sleep and poor sleep quality is associated with insulin resistance.  Over the last few years, clinical studies established a link between obstructive sleep apnea (OSA) and type 2 diabetes. As a result of this research, the International Diabetes Federation (IDF) now recommends that all patients presenting with either condition should be evaluated for the other. The IDF also encourages health care providers to familiarize themselves with the clinical connections between the two conditions. 

Research demonstrates that up to 50% of patients with diabetes suffer from sleep apnea.^1,2  Other studies  show an independent association between forms of OSA and both insulin resistance and glucose intolerance.^{3 ,4} While both conditions are most often associated with obesity, one study has also demonstrated a relationship between OSA and glucose-insulin metabolism irrespective of age or obesity.⁵ This article addresses the details of a number of studies linking OSA and diabetes, as well as further discussing the new IDF recommendations regarding screening for both conditions. In light of the IDF’s recommendation and the clinical evidence presented here, physicians should make SDB-screening a priority in the management of their patients with diabetes.

What is sleep-disordered breathing? 

Obstructive sleep apnea (OSA) is a condition in which patients stop breathing for 10 seconds or more during sleep, sometimes hundreds of times in a night. Studies indicate that one in five adults suffer from sleep apneas, ranging in severity from mild to potentially lethal.⁶ Approximately one quarter of men and one in ten women are affected by some form of sleep-disordered breathing (SDB), of which OSA is the most common. OSA increases in prevalence with the age of the patient; some degree of breathing cessation is experienced during sleep by nearly one-third of men between the ages of 50 and 60.⁷ In spite of its prevalence as a condition, studies indicate that as many as 80% of those suffering from SDB go undiagnosed. ⁶  

Common signs and symptoms of sleep apnea include:

Excessive daytime sleepiness

Snoring

Morning headaches

Neck size of greater 17 in for males, 16 in for females

Obesity

Hypertension 

Excessive daytime sleepiness

Poor motivation 

Memory loss/difficulty concentrating – decreased cognitive functioning

Depression

As the above symptoms suggest, OSA can lead to decreased productivity at work and in the home, as well as a loss of general quality of life. But even more troubling from a public health perspective, OSA has demonstrated links with other serious health risks. Comorbidities for OSA include heart disease, high blood pressure, stroke, and obesity.^8-13 Diabetes is also a comorbidity, and several recent studies increasingly indicate not only the link between diabetes symptoms and OSA, but the positive effects of CPAP treatment in reducing some of these symptoms.

Studies Detail Mechanisms Linking OSA and Diabetes

Since 2003 a series of clinical studies have solidified the connection between OSA and type 2 diabetes.

One study found evidence that OSA impairs insulin sensitivity in obese patients. Of nearly 60 obese patients, approximately half of whom suffered from OSA, researchers found that the obese patients also suffering from OSA were markedly less sensitive to insulin than the patients with simple obesity, regardless of adiposity. Researchers concluded that this worsening in insulin sensitivity in OSA patients is likely to account for the increases in vascular risk for these patients as opposed to those suffering from obesity alone. ¹⁴

A 2004 study found that CPAP treatment rapidly improves insulin sensitivity in patients with OSA. The study measured insulin sensitivity in 40 patients after 2 days of CPAP therapy and then again after 3 months of uninterrupted continual therapy.  Surprisingly, there was a significant increase in insulin sensitivity in subjects after only 2 days of treatment. The increase was also found to be sustained after the 3 months of continuous CPAP usage.  Based on this evidence, researchers concluded that sleep apnea is an independent risk factor for increasing insulin resistance. ¹⁵

Another study has found impaired glucose homeostasis to be related to SDB. The study demonstrated that initiating CPAP treatment improved glycemic control in a group of 24 very obese patients with type 2 diabetes. These results led the researchers suggest that CPAP can be an important therapeutic approach for diabetics with SDB. ¹⁶

An important study from 2007 documents the widespread prevalence of OSA in the population of adults with type 2 diabetes. In this study of 279 diabetic patients, nearly 50% were found to suffer from OSA as well. The study also identified factors that may be associated with its presence in the population, including male sex, an age of 62 years or older, obesity, snoring, and reports of breathing cessation during sleep. As a result of the study the researchers recommended that screening for OSA be considered for all patients with type 2 diabetes. ¹

Yet another study further documents a clear role for slow-wave sleep (SWS) in the maintenance of glucose homeostasis. The study found a remarkably consistent 25% decrease of insulin sensitivity by in a population of young, lean males after three nights of suppressed SWS. This change in insulin sensitivity is comparable to that associated with a bodily weight increase of 8-13kg. This decrease leads to a reduced glucose tolerance and an increased risk of diabetes. The data suggests that reduced sleep quality with low levels of SWS may contribute to an increased risk of diabetes in aging and obese patients. ¹⁷

International Diabetes Federation recommends OSA/diabetes screening

In light of compelling clinical research such as that detailed above, a consensus statement was presented at the June 7 meeting of the American Diabetes Association (ADA) recommending that all patients receiving treatment for either OSA or type 2 diabetes should be screened for the other condition. This statement, published in Diabetes Research and Clinical Practice, was crafted by the consensus of 22 world-wide leaders in diabetes and sleep apnea research from around the world who were brought together by the International Diabetes Federation (IDF), a global alliance of diabetes associations.

The consensus statement highlights the connections between the two conditions and makes several specific recommendations to physicians. First, it recommends that patients with type 2 diabetes should be assessed for symptoms of OSA. It also states that owing to the established benefits of therapy, there should be a low threshold for referral to establish a diagnosis. The statement also names CPAP as the current best treatment for moderate to severe sleep apnea. Finally, it suggests that all patients already diagnosed with sleep apnea should be routinely screened for markers of metabolic disturbance and cardiovascular risk.

SDB Screening and Referral

The easiest way to screen for OSA is to offer a simple questionnaire such as the Epworth Sleepiness Scale (ESS) or the Berlin Questionnaire. Patients who score positive via one of these screening methods should be referred for a diagnostic study, either in-lab, or, as CMS has recently approved the use of portable devices, patients may also undergo an in-home test with a portable diagnostic device. After completing a diagnostic study, the patient can then be referred for appropriate treatment.

A variety of treatments exist for those diagnosed with OSA at the sleep lab. A wide variety of CPAP devices, the gold standard for diagnosis, exist to provide customized therapy for the individual needs of most if not all patients.

Conclusion 

The recent IDF recommendation crafted by key leaders in the field of diabetes and sleep apnea further solidifies a well-established clinical link between these two conditions, and indicates that screening and treatment for diabetes and sleep apnea should go hand in hand. Furthermore, clinical evidence shows that CPAP treatment may improve diabetes outcomes in patients with diabetes and OSA. With these demonstrated links and benefits, and considering the ease and availability of simple and inexpensive sleep apnea screening tools, physicians treating patients with diabetes should make screening a routine part of clinical practice.

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