Nov. 28, 2000 ROCHESTER, MINN. -- People with obstructive sleep apnea (OSA) are likely to have a blood vessel impairment that may cause daytime blood pressure elevation and may lead to heart disease, according to a new Mayo Clinic study published this week in Circulation. An estimated 15 million Americans -- three-fourths of them men -- suffer from sleep apnea, but only about ten percent have been diagnosed and treated.
The study, conducted in collaboration with University of Iowa researchers, compared endothelial function in healthy obese subjects with sleep apnea with a closely matched control group without sleep apnea. The endothelium is a layer of cells that lines blood vessels and regulates blood pressure by causing vessels to dilate.
"We know that high blood pressure, diabetes, congestive heart failure and high cholesterol levels damage the endothelium, and that this endothelial impairment in turn may lead to blood pressure elevation and further vessel damage," says Virend Somers, M.D., a Mayo Clinic cardiologist and the senior investigator in the study. "This study shows that sleep apnea also is an independent cause of endothelial impairment, even in the absence of other factors. It suggests that sleep apnea in otherwise healthy individuals may set in motion a long-term cycle of endothelial damage, hypertension and heart disease."
People with sleep apnea typically stop breathing dozens or even hundreds of times during the night as their airway collapses like a wet soda straw. Researchers believe the combination of oxygen deprivation and the extremely high nighttime blood pressure caused by sleep apnea may be responsible for the endothelial damage observed in the study.
Results showing restoration of endothelial function by correcting other risk factors lead researchers to believe that treating OSA may have a similar effect. "Since treating high blood pressure and hypertension has been shown to improve endothelial function, it seems likely that eliminating the nightly blood pressure spikes and oxygen shortages caused by OSA also will help," says Dr. Somers. "Patients who receive treatment also typically feel better rested and are more alert, and therefore are less likely to get in an accident than those who continue to suffer sleep deprivation."
Dr. Somers says the study highlights the widespread cardiovascular effects of sleep apnea and the need for people to learn about it and watch for its symptoms. "Most cases of sleep apnea are first noticed when the patient falls asleep during the day, or by a woman seeing her husband stop breathing at night. The good news is that in many cases patients can reduce or eliminate the problem by losing weight, sleeping on their side, and avoiding alcohol and sleeping pills. Others find relief through a continuous positive airway pressure (CPAP) device, which keeps the airway from collapsing. While these treatments are not perfect, they can help the majority of sleep apnea sufferers. This new study gives one more important reason for people who suspect they have sleep apnea to seek medical attention."
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