HEALTH NEWS

Study Title:

Decreased Slow Wave Sleep Increases Risk of Developing Hypertension in Elderly Men

Study Abstract

The importance of sleep to health and cardiovascular disease has become increasingly apparent. Sleep-disordered breathing, sleep duration, and sleep architecture may all influence metabolism and neurohormonal systems, yet no previous study has evaluated these sleep characteristics concurrently in relation to incident hypertension. Our objective was to determine whether incident hypertension is associated with polysomnography measures of sleep-disordered breathing, sleep duration, and sleep architecture in older men. Participants were 784 community-dwelling, ambulatory men ≥65 years of age (mean age: 75.1±4.9 years) from the Outcomes of Sleep Disorders in Older Men Study who did not have hypertension at the time of their in-home polysomnography sleep studies (2003–2005) and who returned for follow-up (2007–2009). Of 784 older men included in this report, 243 met criteria for incident hypertension after a mean follow-up of 3.4 years. In unadjusted analyses, incident hypertension was associated with increased hypoxemia, increased sleep stages N1 and N2, and decreased stage N3 (slow wave sleep [SWS]). After adjustment for age, nonwhite race, study site, and body mass index, the only sleep index to remain significantly associated with incident hypertension was SWS percentage (odds ratio for lowest to highest quartile of SWS: 1.83 [95% CI: 1.18 to 2.85]). No attenuation of this association was seen after accounting for sleep duration, sleep fragmentation, and indices of sleep-disordered breathing. Percentage time in SWS was inversely associated with incident hypertension, independent of sleep duration and fragmentation, and sleep-disordered breathing. Selective deprivation of SWS may contribute to adverse blood pressure in older men.

From press release:

Reduced slow wave sleep (SWS) is a powerful predictor for developing high blood pressure in older men, according to new research in Hypertension: Journal of the American Heart Association.

SWS, one of the deeper stages of sleep, is characterized by non-rapid eye movement (non-REM) from which it's difficult to awaken. It's represented by relatively slow, synchronized brain waves called delta activity on an electroencephalogram. Researchers from the Outcomes of Sleep Disorders in Older Men Study (MrOs Sleep Study) found that people with the lowest level of SWS had an 80 percent increased risk of developing high blood pressure.

"Our study shows for the first time that poor quality sleep, reflected by reduced slow wave sleep, puts individuals at significantly increased risk of developing high blood pressure, and that this effect appears to be independent of the influence of breathing pauses during sleep," said Susan Redline, M.D., the study's co-author and Peter C. Farrell Professor of Sleep Medicine in the Department of Medicine at Brigham and Women's Hospital and Beth Israel Deaconess Medical Center, Harvard Medical School in Boston, Mass.

Men who spent less than 4 percent of their sleep time in SWS were significantly more likely to develop high blood pressure during the 3.4 years of the study. Men with reduced SWS had generally poorer sleep quality as measured by shorter sleep duration and more awakenings at night and had more severe sleep apnea than men with higher levels of SWS. However, of all measures of sleep quality, decreased SWS was the most strongly associated with the development of high blood pressure. This relationship was observed even after considering other aspects of sleep quality.

Participant's average body mass index was 26.4 kg/m2. But the study effects of SWS were independent of obesity and continued to be seen after considering the effects of obesity.

The researchers conducted comprehensive and objective evaluation of sleep characteristics related to high blood pressure in 784 men who didn't have hypertension. They were studied in their own homes using standardized in-home sleep studies, or polysomnography, with measurement of brain wave activity distinguishing between REM and non-REM sleep, and sleep apnea through measurement of breathing disturbances and level of oxygenation during sleep.

Using a central Sleep Reading Center directed by Redline, the researchers assessed a wide range of measurements of sleep disturbances, such as frequency of breathing disturbances, time in each sleep state, number of nighttime awakenings, and sleep duration.

The participants were an average 75 years old and almost 90 percent were Caucasian. All were healthy and living in one of six communities, geographically representative of the United States: San Diego, Calif.; Palo Alto, Calif.; Pittsburgh, Pa.; Minneapolis, Minn.; Birmingham, Ala.; and Portland, Oregon. The study was coordinated by California Pacific Medical Center.

Generally, older men and women are more likely to develop high blood pressure than younger people. Sleep disorders and poor quality sleep are more common in older adults than in younger ones. Obesity is also associated with hypertension, researchers said.

In the Sleep Heart Health Study, another large cohort study, researchers found that men were more likely to have less SWS than women. Men were also at an increased risk of high blood pressure when compared to women. The current study raises the possibility that poorer sleep in men may partly explain the male gender predisposition to high blood pressure.

"Although women were not included in this study, it's quite likely that those who have lower levels of slow wave sleep for any number of reasons may also have an increased risk of developing high blood pressure," Redline said.

Slow wave sleep has been implicated in learning and memory with recent data also highlighting its importance to a variety of physiological functions, including metabolism and diabetes, and neurohormonal systems affecting the sympathetic nervous system that contribute to high blood pressure, researchers said.

Good quality sleep is the third pillar of health, Redline said. "People should recognize that sleep, diet and physical activity are critical to health, including heart health and optimal blood pressure control. Although the elderly often have poor sleep, our study shows that such a finding is not benign. Poor sleep may be a powerful predictor for adverse health outcomes. Initiatives to improve sleep may provide novel approaches for reducing hypertension burden."

Study Information

Maple M. Fung, Katherine Peters, Susan Redline, Michael G. Ziegler, Sonia Ancoli-Israel, Elizabeth Barrett-Connor, Katie L. Stone, for the Osteoporotic Fractures in Men Research Group.
Decreased Slow Wave Sleep Increases Risk of Developing Hypertension in Elderly Men
Hypertension
2011 August
Department of Medicine at Brigham and Women's Hospital and Beth Israel Deaconess Medical Center, Harvard Medical School in Boston, Mass.