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| |  Disordered Breathing Linked To High Risk Of Hypertension CHICAGO, IL -- April 11, 2000 -- An association is found between sleep-disordered breathing and hypertension in a large multicenter study, according to an article in the April 12, 2000, issue of The Journal of the American Medical Association (JAMA). F. Javier Nieto, M.D., Ph.D., from Johns Hopkins School of Hygiene and Public Health in Baltimore and colleagues report on the association between hypertension and sleep-disordered breathing, which includes sleep apnea (a complete or almost complete cessation of airflow during sleep; often characterized by snoring). The researchers report on data from 6,132 participants 40-years old and older who participated in the Sleep Heart Health Study, a multicenter study that recruited patients with sleep apnea from other studies in order to examine the associations between sleep apnea and cardiovascular conditions. The researchers found that the prevalence of hypertension (defined as resting blood pressure at least 140/90 or use of antihypertensive medication) increased as average sleep-disordered breathing episodes per hour increased. Participants in the category of highest frequency of breathing disorders (30 or more apnea-hypopnea index [AHI] episodes per hour) had a higher risk (adjusted odds ratio of 1.37) of experiencing hypertension than those in the lowest category (less than one and a half AHI episodes per hour). The crude rates of hypertension ranged from 43 percent for those in the lowest AHI category (less than 1.5 per hour) to 67 percent for those in the highest AHI category (30 or more per hour). "After controlling for the main potential cofounders (age, sex, BMI [body mass index] and other measures of adiposity [fat just beneath the skin]) as well as for other potentially relevant variables (alcohol intake, smoking), high levels of AHI or sleep time below 90 percent oxygen saturation were associated with greater odds of hypertension in a dose-response fashion [the higher the levels of AHI or sleep time below 90 percent oxygen saturation the higher the blood pressure levels]." The researchers used the AHI to assess sleep-disordered breathing. The AHI included the average number of apnea episodes plus the average number of hypopnea episodes per hour of sleep. Hypopnea was defined as a 30 percent or greater decrease in airflow or a 30 percent or greater decrease in chest and abdomen movement accompanied by a 4 percent or greater decrease in oxygen saturation in the blood. The researchers measured AHI using a polysomnography during a one night home visit to measure a number of factors including airflow and chest and abdominal movement. The participants also completed a self-administered questionnaire about sleep habits that included questions about awareness of a history of snoring, awareness of sleep apnea, awareness of treatment for sleep apnea and experience of sleepiness. The researchers also measured the number of arousals from sleep per hour and the percentage of sleep time where the oxygen saturation was below 90 percent. Related Link: The Journal of the American Medical Association (JAMA).
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