New research says not getting enough slow wave sleep (SWS) is an accurate predictor for developing high blood pressure in older men. Published in Hypertension: Journal of the American Heart Association, this study shows for the first time a link between poor quality of sleep and risk of developing high blood pressure.

SWS is one of the deeper stages of sleep and is distinguished by non-rapid eye movement (non-REM). In this type of sleep, it is difficult to wake up. On an electroencephalogram, SWS sleep registers delta activity: slow, synchronized brain waves. According to the researchers from the Outcomes of Sleep Disorders in Older Men Study (MrOs Sleep Study), people that experiences the lowest level of SWS displayed an 80 percent higher 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," explained 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.

If men spend less than 4 percent of their nightly sleep time in SWS, then they are much more likely to develop high blood pressure. If men had reduced SWS, they typically also experienced poorer sleep quality, as measured by shorter sleep durations and more often nighttime awakenings, and they had more sleep apnea when compared to men with higher levels of SWS. Although, decreased SWS was the aspect most associated with risk of high blood pressure when compared with all other measures of sleep quality. This relationship was even observed after the data were corrected for other significant facet of sleep quality.

"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," said Redline.

Recently, SWS has been shown to be important in both learning and memory. The researchers pointed out that recent data have underscored the importance of SWS to physiological functions as well, including diabetes, metabolism, and neurohormonal systems affecting the sympathetic nervous system, which contributes to high blood pressure.

Quality sleep is the third pillar of health, Redline explained. "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."