Obstructive sleep apnea affects 24 percent of men and 9 percent of women in the general population. But studies suggest that the majority of people with type 2 diabetes, especially those who are obese, may have some degree of sleep apnea.

It's not clear why people with type 2 diabetes are more likely to be affected. Some scientists believe that obstructive sleep apnea and type 2 diabetes simply share a common factor: obesity, which is closely linked to both conditions. But while obesity is undoubtedly related to obstructive sleep apnea, recent research suggests that this common breathing disorder may make it harder to manage blood glucose even if you don't carry a lot of body fat.

Evidence of this comes from both the laboratory and from research in humans. For example, studies of obese and lean laboratory mice have shown that artificially inducing obstructive sleep apnea by depriving the animals of oxygen for short intervals during their usual sleep time caused them to develop insulin resistance.

Small studies in healthy normal-weight humans have also found that brief periods of oxygen deprivation (intermittent hypoxia) interfere with glucose metabolism. Another small experiment found that suppressing deep sleep in healthy humans for three nights in a row reduced insulin sensitivity by 25 percent.

A larger study reported in 2010 revealed that the severity of obstructive sleep apnea is closely related to glucose control. Researchers compared 14 people with type 2 diabetes who slept soundly and silently at night with 46 who also had obstructive sleep apnea. They found that people who had mild sleep apnea (five to 15 apnea episodes per hour) had HbA1c levels that were 1.5 percent higher, on average, than the sound sleepers. People with severe sleep apnea (30 or more episodes per hour) were much worse off—their HbA1c levels were nearly 4 percent higher than those without sleep apnea, after accounting for differences in characteristics between the groups.

These findings are intriguing, but more research is needed before investigators can definitively conclude that obstructive sleep apnea adversely affects glucose control—and if proven, how it exerts that effect. One possibility: Sleep deprivation and frequent breathing stoppages put the body in a state of stress, which impacts glucose metabolism and precipitates the development of insulin resistance.

Publication Review By: Rita Rastogi Kalyani, M.D., and Simeon Margolis, M.D., Ph.D.

Published: 24 Jul 2013

Last Modified: 11 Sep 2015