The findings contradict years of studies that have attributed the changes – which include signs of inflammation, generation of destructive free radicals, and vessel stiffness – directly to excess fat tissue.
“Considering the difficulty of losing weight, the study suggests that treating sleep apnea may be a good alternative to reduce some of the risk of cardiovascular disease,” says lead author Sanja Jelic, MD, Irving Assistant Professor of Medicine.
The study appears in the March 2 issue of the journal Circulation.
“Obstructive sleep apnea is like putting a pillow over someone’s face five to more than 100 times an hour while they sleep,” Dr. Jelic says. “Every time muscles in the throat collapse, airflow is blocked and oxygen levels drop.”
Researchers estimate about 25 percent of the U.S. population has obstructive sleep apnea, but only 1 out of 10 has been diagnosed. Only half of those receive treatment.
Untreated sleep apnea has been linked to high blood pressure, stroke, and cardiovascular disease, though the reasons have been unclear.
Two years ago Dr. Jelic found that sleep apnea appears to lead to atherosclerosis in a similar way as obesity: by inflaming blood vessels, stiffening the vessel walls, and generating destructive free radicals.
Since sleep apnea and obesity often go hand-in-hand, Dr. Jelic set out to determine if the two together make conditions inside the vessels even worse.
In the study, 71 obese and normal weight participants spent a night in Columbia’s Sleep Disorders Center, where 38 were diagnosed with obstructive sleep apnea. The researchers scraped cells from the lining of a vein in the lower arm and looked for signs that indicate the health of the vessels, such as markers of inflammation and free radical production.
“We thought that sleep apnea would add to obesity’s effect on the vessels, but we were surprised to see that apnea accounted for the entire effect,” Dr. Jelic says. “The cells from obese people looked just like cells from people of normal weight. The only cells that were impaired were from people with sleep apnea.”
For these people, four weeks of treatment with continuous positive airway pressure (CPAP) completely erased the signs of impairment.
Dr. Jelic says that previous studies that linked vessel health to obesity did not determine if participants had obstructive sleep apnea. “It’s likely that most of the obese people in these studies had undiagnosed sleep apnea, and the apnea contributed significantly to the link, not the obesity itself.”
“We’re not saying that sleep apnea completely explains why obesity is linked with cardiovascular disease – obesity probably has other effects on blood vessels – but that sleep apnea is a significant contributor. And it’s treatable.”