The Doctor Weighs In

By Pat Salber, MD

We have known about the association between snoring and obesity for a long time. But we now know that sleep-disordered breathing (SBD) -- a sleep disturbance characterized by snoring and episodes of apnea or not breathing for periods of time -- is linked, independent of obesity, to insulin resistance, abnormal glucose metabolism, and Type 2 diabetes.

Sinziana Seicean, MD, MPH and colleagues published results of the Sleep Heart Health Study in the May 2008 issue of Diabetes Care. They studied 209 normal weight and 1,036 overweight/obese individuals who had a diagnosis of SDB, but did not have a diagnosis of diabetes. They found that SDB was associated with all of the manifestations of impaired glucose metabolism, including impaired fasting glucose, impaired glucose tolerance, and occult diabetes. The magnitude of the association between SDB and abnormal glucose metabolism was the same regardless of whether the individual was normal or overweight/obese.

This suggests that obesity is not the common cause of both insulin resistance and sleep-disordered breathing. Rather there appears to be an independent association between SDB and impaired glucose metabolism that is not explained by adiposity.

The authors suggest that the association of SDB with glucometabolic disturbances may relate to the “often-profound physiological stresses that occur overnight with sleep apnea.” They suggest that these stresses may transiently increase autonomic sympathetic activity, increase outpouring of the stress hormone, cortisol, and a decrease insulin sensitivity. Indeed, they point out that a human study of people with sleep apnea demonstrated improved insulin sensitivity after treatment of the SDB with continuous positive airway pressure (CPAP)

Why is this study important? Because it means that individuals with SDB who are normal weight may be at risk of impaired glucose metabolism. It also suggests that therapy aimed specifically at SDB and not just at obesity may be indicated to reverse that risk.

To learn if you are at risk of having SDB, answer the following questions based on the Berlin Questionnaire: