"Sleep apnea can have significant consequences on a person's physical health, and this study shows once again that treatment may lessen those risks," said lead researcher Daniel Norman, M.D., Fellow in Pulmonary and Critical Care at the University of California San Diego Medical Center.
In obstructive sleep apnea, the upper airway narrows, or collapses, during sleep. Periods of apnea end with a brief partial arousal that may disrupt sleep hundreds of times a night. More than half of those with sleep apnea also have high blood pressure, and their blood pressure does not fall during sleep as it does in most people.
The most widely used treatment for sleep apnea is a technique called nasal CPAP, for continuous positive airway pressure, which delivers air through a mask while the patient sleeps. It has proved successful in many cases in providing a good night's sleep and preventing daytime accidents due to sleepiness. Supplementary oxygen is sometimes used as a treatment for sleep apnea.
The researchers studied 46 patients with moderate to severe sleep apnea. They were randomly assigned to receive either CPAP treatment, fake CPAP or supplemental nighttime oxygen through a face mask. All patients were hooked up to a 24-hour ambulatory blood pressure monitor, which consists of a small machine strapped to the patient's torso that attaches to an arm cuff. The cuff automatically inflates and deflates to measure patients' blood pressure.
After two weeks, patients who received the real CPAP treatment had significant reductions in blood pressure during the day and night. Nighttime oxygen therapy did not affect blood pressure.
"There has been some controversy over how sleep apnea causes elevated blood pressure," Dr. Norman said. "Doctors don't know if it is due to drops in oxygen levels or arousals from sleep. Our study indicated that correcting drops in oxygen levels alone may not be enough to reduce blood pressure."
The National Heart, Lung, and Blood Institute estimates that 18 million Americans have sleep apnea. Men are more susceptible than women.
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