People with sleep apnea are at special risk for hypertension, according to a study funded by the National Heart, Lung, and Blood Institute (NHLBI) of the National Institutes of Health.
Data from the NHLBI's "Sleep Heart Health Study" (SHHS), which are reported in the April 12, 2000 issue of the Journal of the American Medical Association, show that middle-aged and older adults with sleep apnea have a 45 percent greater risk of hypertension than people without the condition.
Hypertension, or high blood pressure, is a major risk factor for cardiovascular disease.
According to NHLBI Director Dr. Claude Lenfant, "This is the first study large enough to examine the relationship between sleep apnea and hypertension, independent of other cardiovascular risk factors. It is extremely important, since hypertension is a major risk factor for cardiovascular disease, which is the leading cause of death in the U.S. today."
"Although these results must be verified, they offer hope that we may be able to reduce cardiovascular mortality in hypertensives by more aggressively diagnosing the apnea," he added.
Approximately 12 million Americans have sleep apnea, a breathing disorder characterized by brief interruptions of breathing during sleep (up to 20-30 breathing pauses per hour, each lasting at least 10 seconds). These breathing pauses are almost always accompanied by loud snoring.
The most common treatment is continuous positive airway pressure (CPAP), a procedure involving use of a face mask which forces air through the nasal passages. Behavioral changes, especially weight loss, are usually recommended as well.
The SHHS involved more than 6,000 adults, ages 40 and over, who were participating in other NHLBI cohort studies of cardiovascular and respiratory disease between 1995-1998.
Sleep apnea was assessed through at-home polysomnography, a test that records a variety of body functions during sleep, such as the electrical activity of the brain, eye movement, muscle activity, heart rate, respiratory effort, air flow, and blood oxygen levels.
Following NHLBI guidelines, hypertension was defined as blood pressure of at least 140/90 mm Hg.
The study showed that the risk of hypertension increased with the severity of the apnea in all participants, regardless of age, sex, race, or weight. The risk was seen even at moderate levels of sleep apnea.
The centers participating in the study were:
Boston University, Boston, MA; Cornell University, New York, NY; Johns Hopkins University, Baltimore, MD; New York University, New York, NY; University Hospital-Rainbow Babies & Children's Hospital, Cleveland, OH; University of Arizona College of Medicine, Tucson, AZ; University of California at Davis, CA; University of Minnesota, Minneapolis, MN; University of Pittsburgh School of Medicine, Pittsburgh, PA; University of Washington, Seattle, WA; and University of Wisconsin, Madison, WI.