April 11, 2000 (Minneapolis) -- If you snore, you might want to wake up to the latest news: those nighttime noises may be more than just an annoyance. In the largest study to date, sleep experts have confirmed that disturbed breathing during sleep is associated with high blood pressure in middle-aged and older persons regardless of race or sex. But the researchers, like others before them, failed to determine the cause -- an important step that can lead to better treatment. The study was published in the April 12 issue of the Journal of the American Medical Association
Researchers have been studying sleep-connected breathing problems since the early 1980s. Sleep apnea -- the obstruction of airflow through the nose and mouth -- takes place during sleep and occurs in one in 10 women and one in four men. Although many people are unaware of their breathing abnormalities, researchers who studied people during slumber have found a link between sleep apnea, snoring, and high blood pressure.
Scientists at Johns Hopkins School of Hygiene and Public Health in Baltimore and elsewhere conducted the largest study on the sleep disorder -- a total of over 6,100 subjects, including men and women over age 40 and of different ethnic backgrounds, were included. F. Javier Nieto, MD, PhD, and colleagues collected data about smoking habits, alcohol use, weight, body mass, and history of snoring. They measured blood pressure and studied the histories of high blood pressure in study participants. A self-administered sleep habits questionnaire helped researchers gather medical history and snoring history. Then, during sleep, monitors measured sleep stages, breathing, and blood pressure.
Researchers found that nearly half of the subjects had more than five episodes of apnea per hour of sleep. More disturbing, the researchers also found "a clear association between increasing frequency of [apnea] events and hypertension," particularly among patients classified as obese.
In the same journal, sleep expert Clifford W. Zwillich, MD, describes the study as "powerful" because information was collected from such a large group, but he also criticizes the trial because the reason for the link remains unknown -- something that has major public health implications, he says.