Slow Wave Sleep Can Predict Hypertension Risk

Kate H. Gamble, Senior Editor
Published Online: Monday, September 12, 2011
Reduced slow wave sleep (SWS) is a powerful predictor for developing high blood pressure in older men, according to study published in Hypertension: Journal of the American Heart Association.

Researchers from the Outcomes of Sleep Disorders in Older Men Study (MrOs Sleep Study) found that individuals with the lowest level of SWS—a deep stage of sleep characterized by non-rapid eye movement (non-REM)—had an 80% 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 study co-author Susan Redline, MD, of Harvard Medical School, in a statement.

Men who spent less than 4% of their sleep time in SWS were significantly more likely to develop high blood pressure during the 3-year 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, the authors noted.

The researchers conducted comprehensive evaluations of sleep characteristics related to hypertension in 784 men who didn’t have high blood pressure. Participants 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.

They found that in general, older men and women are more likely to develop hypertension than younger individuals. It was also determined that sleep disorders and poor quality sleep are more common in older adults, and that obesity is associated with hypertension.

Slow wave sleep has been shown to affect 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.

“People should recognize that sleep, diet and physical activity are critical to health, including heart health and optimal blood pressure control,” said Redline. “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.”

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