Daytime sleepiness caused by the nighttime breathing disorder sleep apnea is nothing to yawn at.

A new study from Canada hints that the risk of diabetes may be two to three times higher among people with severe sleep apnea who also suffer daytime sleepiness.

“This raises the intriguing possibility that sleepiness (or sleep disruption) may have an independent effect on the risk for diabetes,” Dr. Willis H. Tsai, of Rockview General Hospital in Calgary, Alberta, noted in an email to Reuters Health.

Obstructive sleep apnea, or OSA, is a disorder in which the tissues at the back of the throat temporarily collapse during sleep, causing repeated stops and starts in breathing during the night. This leads to poor-quality sleep and, often, daytime drowsiness.

Tsai’s team looked at associations between diabetes and OSA among 1,346 men and 803 women assessed for OSA when they were about 50 years old on average.

Sleep evaluations showed that 25 percent had severe OSA - that is 30 or more bouts of disturbed breathing per night. Another 21 percent, without OSA, suffered 5 or fewer of these bouts nightly. The remaining participants had between 6 and 29 nighttime bouts of disturbed breathing, and were classified as having mild to moderate OSA.

About 8 percent of the participants in the study also reported having diabetes. And those with severe OSA were much more likely to have diabetes even after the investigators allowed for other OSA risk factors such as age, body weight, gender, neck circumference, and smoking status.

Tsai and colleagues note the increased risk for diabetes was primarily among participants with severe OSA who reported daytime sleepiness.

Severe OSA has been linked to an increased risk of heart disease and death. More recently, OSA has been linked to resistance to the blood-sugar-lowering hormone insulin. “Insulin resistance” is a precursor to diabetes.

If further research confirms the link between OSA and diabetes seen in the current study, a history of daytime sleepiness might help doctors identify OSA patients at increased risk for developing diabetes, Tsai’s group suggests.

SOURCE: Thorax, October 2009.