CPAP Linked to Lower Hypertension Risk, but Questions Remain
By Salynn Boyles
WebMD Health News
Reviewed by Laura J. Martin, MD
Another study that included patients who used a CPAP machine for more than four hours a night, but not less, appeared to have a lower high blood pressure risk.
CPAP opens airways by forcing air into the nostrils through a mask worn while sleeping.
The studies, published today in the Journal of the American Medical Association, add to the evidence that positive air pressure treatment lowers heart risk in patients with obstructive sleep apnea -- but important questions remain, experts say.
"We know that obstructive sleep apnea is a potential cause of high blood pressure, and we know that CPAP use is associated with reductions in blood pressure in people with hypertension," says sleep specialist Vishesh K. Kapur, MD, of the University of Washington, Seattle. "And now there is reasonable evidence that this treatment can prevent high blood pressure in patients who don't already have it."
Sleep Apnea Often Not Diagnosed
Almost 1 in 5 adults in the United States has mild to severe sleep apnea, but only about 10% have been diagnosed with the disorder.
CPAP has been shown to improve quality of life and daytime sleepiness, but adherence is an issue because many patients find the masks too uncomfortable to wear.
While studies strongly suggest a causal role for obstructive sleep apnea in high blood pressure, confirming the association has been difficult because the disorder is common in people with other risk factors for high blood pressure, such as obesity.
In one of the newly published studies, researchers from Lleida, Spain's, Institut de Recerca Biomedica recruited around 700 sleep apnea patients and treated half with CPAP.
At a follow-up of around four years, patients treated with CPAP had a slightly lower incidence of high blood pressure, heart attack, stroke, and other heart-related events than patients not treated with CPAP, but the difference was not found to be significant -- a finding the researchers themselves admitted, though, might have had a more positive outcome if the study had been longer or had more participants.
Use of CPAP for more than four hours per night did however appear to lower high blood pressure risk, suggesting that adherence with treatment may be critical in this group of patients.
CPAP: If at First You Don't Succeed…
The second study included close to 1,900 sleep apnea patients without high blood pressure who were followed for an average of 11 years.
Researchers from Zaragoza, Spain's, Hospital Universitario Miguel Servet found that patients who were prescribed CPAP but declined the treatment had about twice the risk for developing high blood pressure as people without sleep apnea.
Patients who were non-adherent with prescribed CPAP therapy had about an 80% greater risk.
Sleep specialist Yosef P. Krespi, MD, of Lenox Hill Hospital in New York City, says adherence with CPAP therapy could be improved if more clinicians worked with patients to get the treatment right.
As many as half of people who try CPAP abandon it after a few days or weeks, studies suggest.
"We used to tell patients who said they couldn't use CPAP not to worry about it," he tells WebMD. "Now we tell them to come back in and we work with them. We can readjust the pressure, change the mask, and even add a humidifier if it is too hot. We can do a lot of tweaking."
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