A national multicenter study which includes researchers at the School of Public Health confirms a possible connection between sleep apnea and hypertension (high blood pressure) in both older and middle-aged adults. The study, which appears in the April 12 issue of Journal of the American Medical Association, found those who suffer from moderate to severe sleep apnea were at increased risk of having high blood pressure.
Sleep apnea, characterized by snoring and frequent pauses in breathing during sleep, is a relatively common condition, most notably in those who are overweight. "As a result of this study, we now believe that sleep apnea may be one of the reasons why overweight people are at increased risk for high blood pressure," said lead author Javier Nieto, an associate professor in the Department of Epidemiology in the School of Public Health. "The connection is important because high blood pressure can lead to serious adverse health consequences, including heart attack, stroke and kidney disease."
The study involved more than 6,000 men and women age 40 or older. The presence of sleep apnea was detected using polysomnography, which simultaneously records brain waves, heart waves, blood oxygen levels and breathing rate while a person sleeps. A team of technicians visited each participant at home in the evening and measured blood pressure and weight, as well as other health parameters, and then connected the person to a sleep monitor. The average number of breathing pauses per hour of sleep was used to measure the degree of sleep apnea.
The results of the study showed that people with more than 30 pauses per hour of sleep were more than twice as likely to suffer from high blood pressure than those with no breathing pauses. An increased risk of high blood pressure was found even at moderate levels of sleep apnea. Since sleep apnea is more common in overweight individuals--who are already at a higher risk of high blood pressure--additional statistical analyses were conducted to control for body weight and waist circumference. Even after controlling for these variables, however, sleep apnea was associated with an increased frequency of high blood pressure.
The authors stressed that because sleep apnea currently goes undiagnosed in most individuals, the study's results emphasized the need for increased awareness of this condition by both patients and physicians. Whereas the current study measured sleep apnea and blood pressure levels at the same time, subsequent studies are being planned to look at whether changes in sleep apnea levels are related to the onset of hypertension or to fluctuations in blood pressure. The authors also noted that since being overweight can cause sleep apnea, the study's results add new urgency to the search for ways of stopping or reversing the obesity epidemic in the United States.
Support for this study was provided by a grant from the National Heart, Lung and Blood Institute of the National Institutes of Health.