To Sleep, Perchance to Beat High Blood Pressure
Study finds mask for sleep apnea also helps hypertension
FRIDAY, Jan. 18, 2002 (HealthDayNews) -- A device that treats those who suffer from sleep apnea may also reduce blood pressure, new research shows.
The drop in blood pressure could translate into a reduced risk of both stroke and cardiovascular disease, says the new study, which appears in this week's issue of The Lancet.
Considered by some to be a breakthrough report, the study is the first of its kind to show that treating sleep apnea -- a nocturnal breathing disorder -- can protect overall good health.
"Sleep apnea is common, an established treatment is available [that is] known to produce improvements in daytime vitality. We have now also established that [this same treatment] reduces blood pressure, and so it reduces the risk of stroke and other cardiovascular risks," says study author Dr. Robert Davies, of the Oxford Sleep Unit of the Oxford Center for Respiratory Medicine in England.
Sleep apnea is caused by a temporary restriction of air flowing from the nose and mouth to the lungs during sleep. It is second only to asthma as a cause of chronic respiratory disease.
It occurs when muscles in the back of your throat become too relaxed during sleep and a portion of your throat partially collapses, blocking the free flow of air. People with sleep apnea can stop breathing for up to a minute or longer, sometimes hundreds of times a night. The problem is worse for overweight people, because excess tissue in the back of the throat can compound the problem.
The device used in apnea treatment is a face mask known as nCPAP -- short for nasal continuous positive airway pressure -- which patients put on every night before going to bed.
"The mask covers the nose, [and] it stops sleep apnea by delivering a raised airway pressure to the throat," says Davies.
While studies have shown the treatment keeps muscles taut, air passages open and the user breathing freely, what doctors say they hadn't proved was whether it also could reduce some of the secondary problems thought to be associated with sleep apnea, such as high blood pressure.
"We always suspected that sleep apnea caused blood pressure to rise, and that treating apnea would help blood pressure to fall, but we never had the proof that this was so," says Dr. Robert Basner, director of the Columbia University Cardiopulmonary Sleep and Ventilatory Disorders Center.
This study, says Basner, is the first to verify what doctors have long suspected. It also justifies the need for treatment, particularly in England, where there has been resistance to the idea that sleep apnea could have long-term health risks, he adds.
"Now we have proof that it does, and this is an important recognition," says Basner.
That study involved 118 men, all diagnosed with severe obstructive sleep apnea. They were randomly assigned to use either working sleep masks or "sham" masks, which looked the same but didn't have any effect on air passages. Neither the men nor the doctors knew who had the real masks.
At the start of the study, the men took a 24-hour blood pressure test using a device that automatically registered readings every 30 minutes. Baseline pressures were recorded for each man.
The following day, sleep masks were distributed and the men were told to use them nightly for four weeks.
At the end of the four-week period, a second wave of 24-hour blood pressure tests were given, and levels were compared to those taken at the start of the study.
The result: Researchers found a significant difference in both systolic and diastolic blood pressure, during sleep time and wake time, in those men who were wearing the "real" masks, when compared with those wearing the "sham" masks.
Those with the most severe sleep apnea were helped the most, say researchers, as were those already taking medication for high blood pressure.
"[The reduction] was seen in all the subjects, but the largest benefits were in patients with severe disease, a fall of 5.5 mmHg -- enough to reduce stroke risk about 25 percent. In subjects also taking drug treatment, [there was] a fall of over 7 mmHg -- enough to reduce stroke risk about 30 percent," says Davies.
While doctors aren't sure why the masks helped pressure drop, Davies suspects it's related to changes in blood gases that occur in conjunction with the apnea.
"Together, they raise activation of the sympathetic nervous system, which in turn secretes hormones such as adrenaline, which is known to raise blood pressure," says Davies. As this hormonal release lasts into the day, blood pressure continues to rise.
"This [action] then returns to normal with treatment," he says.
Basner agrees, adding that long-term studies are likely to show an even greater decrease in pressure.
"I think that perhaps the longer the treatment is used, the more reduction in blood pressure we will see -- which, in turn, will reduce the risk of stroke and heart attack even more," he says.
What To Do
Symptoms of sleep apnea include snoring, daytime sleepiness, reduced levels of oxygen in the blood and increased blood pressure and risk of cardiovascular disease.
To learn more about sleep apnea, visit The American Sleep Apnea Association..
To take a free self-test to determine whether you might have sleep apnea, visit Sleepnet.
If you want to learn more about how high blood pressure affects your health, visit The National Heart, Lung and Blood Institute.