The Sleep-Hypertension Connection

By Jessica Girdwain

Limited slow-wave sleep may put elders at risk of developing hypertension, according to new research.

Lack of adequate sleep can do more than just leave older adults perpetually exhausted. It can also increase an elder’s risk of developing high blood pressure, according to a new study published in Hypertension.

Researchers looked at 784 men over the age of 65 who did not have hypertension at the beginning of the research period when they took an in-home polysomnography sleep exam as part of the Outcomes of Sleep Disorders in Older Men Study. Researchers followed up with the men 3.4 years later and discovered that the individuals who logged the least amount of slow-wave sleep were at the greatest risk of developing hypertension. Even after adjusting for other factors such as sleep duration and sleep-disordered breathing, the biggest factor in developing hypertension remained the amount of slow-wave sleep.

Slow-wave sleep is known as the restorative phase of sleep, and elders get less of it, partly because they may suffer from sleep disorders such as sleep apnea or restless leg syndrome (RLS). “Those conditions reduce the amount of deep sleep and may also produce certain stresses on the body, like falling oxygen levels in sleep apnea or surges in the sympathetic nervous system or adrenaline in terms of RLS,” says study coauthor Susan Redline, MD, MPH, a researcher in the division of sleep medicine at Brigham and Women’s Hospital in Boston. Other issues such as obesity and medications can have an effect on both sleep quantity and quality.

A reduction in slow-wave sleep disrupts the distinct—and critical—physiological stages a body cycles through during the night. Blood pressure typically decreases 10% to 20% compared with daytime levels, explains Alberto Ramos, MD, an assistant professor of clinical neurology and codirector of the sleep medicine program at the Miller School of Medicine at the University of Miami. Heart rate slows and adrenaline levels and nervous system activity drop. Sleep interruptions prevent this blood pressure decline. In other words, older adults with fragmented sleep maintain their daytime blood pressure during the night, preventing arteries from getting enough time to rest and increasing the likelihood that elders will develop hypertension at night, which eventually translates into daytime hypertension, he says.

Over time, the men in the study developed changes in their blood vessels that led to high blood pressure, Redline adds. Another explanation, she says, is that unfavorable changes in cortisol and insulin levels result from poor sleep quality, impacting blood vessels.

Slow-wave sleep naturally declines with age, starting when a person is in his or her late 30s or early 40s, and is lower in men than women. “This is something that will happen to most people,” says Ramos. “We don’t know if you can get it back or stop the decrease, but experts theorize that if patients keep themselves healthy and take fewer medications, they’ll be able to maintain a healthy pattern of sleep throughout their lifetime.”

Monitor Patients’ Sleep Patterns
There are a few ways health practitioners can help patients achieve good-quality sleep, says Redline. “Doctors should be on the lookout for patients with sleep disorders or symptoms of sleep disorders, like snoring or daytime sleepiness,” she says. Treat exams as an opportunity to screen for issues like sleep apnea. 

Elders tend to wake up often during the night. “So it’s important to know that it’s not about the hours they report that they’re in bed but the hours that they are actually sleeping and how good quality those hours are,” Ramos says. “Pay attention to—and encourage older adult patients to report—changes in their sleeping habits, like snoring, moving too much when dreaming or ‘acting out dreams,’ and not feeling refreshed upon waking. Consider giving them a referral to a sleep specialist, if necessary.”

Ramos notes that treating sleep apnea can be an effective means of reducing blood pressure. “There are studies showing that treating sleep apnea leads to better quality sleep, helping blood pressure regulate throughout the day,” he says. It makes such a big difference that “many times, patients who are on two or three blood pressure medications can go down to one medication.”

Other factors that may help include making sure patients are maintaining a regular sleep schedule or offering to help them determine ways to develop one. They should have regular bedtimes and wake times, and sleep for seven to eight hours per night. Also, take the time to look at their medications, especially if they are complaining of sleep issues, because side effects of many medications produce sleep disruption. When appropriate, take care to prescribe medications that exert the least impact on sleep. “Many sleeping pills are actually sleep disruptors,” Redline warns.

Patients should avoid sleep-disrupting substances such as alcohol or caffeine from three to five hours before bedtime. Communicate to patients that both alcohol and caffeine consumed close to bedtime can cause them to wake up throughout the night and experience more fragmented sleep. 

Increasing the amount of exercise or doing more activities that challenge cognition may also improve slow-wave sleep, says Redline. “Walking is a great way to improve the amount of slow-wave sleep and is a very cheap way to do it, too,” Ramos adds.

Medications for insomnia that improve slow-wave sleep are currently in the developmental stage, according to Ramos, though more tests are needed to determine how effective they will be.

— Jessica Girdwain is a Chicago-based freelance writer who has contributed health-related articles to several national magazines.