August 30, 2011 — In men 65 years and older, increased percentage of time spent in slow-wave sleep appears to be associated with a lower risk for incident hypertension, according to new research findings.
Maple M. Fung, MD, with the San Diego Veterans Affairs Healthcare System, Medicine Service, in San Diego, California, and colleagues reported the findings online August 29 in Hypertension.
According to the researchers, sleep-disordered breathing (SDB), which includes obstructive sleep apnea, sleep deprivation, and/or short sleep duration, is strongly associated with hypertension. "To our knowledge, a comprehensive evaluation of sleep characteristics and incident HTN [hypertension] in an elderly cohort has not been reported."
The current study sought to determine whether incident hypertension is associated with SDB, sleep duration, and sleep architecture in 784 community-dwelling men at least 65 years old (mean age, 75.1 ± 4.9 years). Participants were recruited from the Outcomes of Sleep Disorders in Older Men ancillary study, and they did not have hypertension when sleep patterns were first recorded with polysomnography.
At a mean follow-up of 3.4 years, 243 of the 784 participants met criteria for incident hypertension. After results were adjusted for age, nonwhite race, study site, and body mass index, only percentage duration of slow-wave sleep showed a significant and inverse association with incident hypertension (odds ratio for lowest to highest quartile of slow-wave sleep, 1.83; 95% confidence interval, 1.18 - 2.85).
"In contrast, indices of breathing disturbances, level of hypoxemia, sleep duration, and arousal index were not independently associated with an increased risk of HTN after considering confounders," Dr. Fung and colleagues note.
According to the researchers, slow-wave sleep is the third and final stage of non-REM sleep and is considered to be the most restorative of the rapid eye movement (REM) and non-REM stages of sleep. Slow-wave sleep has also been linked to many health benefits, including enhanced cognitive skills, positive changes in glucose metabolism, and decreased heart rate and blood pressure.
In this study, men classified in the lowest quartile of slow-wave sleep spent less than 4.1% of their total sleep in this restorative phase of sleep, whereas men in the highest quartile spent more than 16.9% of total sleep time in this phase.
"This article adds to the growing body of literature that associates sleep architecture with metabolic and physiological changes that may reflect altered neurohormones and inflammatory markers," they add. "Further studies are necessary to confirm these observations, elucidate the causal pathways, and determine whether modifications in (slow-wave sleep) improve HTN."
The National Heart, Lung, and Blood Institute provides funding for the Osteoporotic Fractures in Men Study sleep ancillary study "Outcomes of Sleep Disorders in Older Men." Dr. Fung has received previous grant support from Forest Laboratories and currently owns stock and is employed by Amgen.
Hypertension. Published online August 29, 2011.
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