Sleep apnea may prove to be a treatable cause of high blood pressure, according to research released today that suggests wearing a special breathing mask at night may protect apnea patients from the hypertension. Most people think of obstructive sleep apnea as a snoring disorder. Although many sufferers snore, apnea is characterized by short episodes in which the patient's upper airway narrows or closes, reducing the flow of oxygen to the body and brain. …Dr. Virend Somers, a sleep apnea and heart disease researcher at the Mayo Clinic in Rochester, Minn., cautioned that the results of the two studies are suggestive "but not definitive that CPAP is protective of the cardiovascular system."