New health guidelines put a spotlight on the link between a good night’s sleep and a healthy heart.
The American Heart Association last month added sleep to its list of factors critical to heart health, a list that includes seven others such as diet, physical activity and blood pressure. The recommendation reflects widening scientific consensus on the role sleep plays in helping prevent heart disease.
“The more we learn, the more we know how instrumental sleep is to heart health,” says Marie-Pierre St-Onge, associate professor of nutritional medicine at Columbia University Irving Medical Center and director of the university’s sleep center.
The heart association recommended adults get seven to nine hours of sleep nightly. Yet many of us are getting less.
More than half of Americans said they had experienced increased sleep disturbances during the pandemic, according to a survey last year commissioned by the American Academy of Sleep Medicine. About 57% said they had more trouble falling or staying asleep; 46% slept less at night and 36% said they had more disturbing dreams.
Some scientists now believe that healthy sleep habits can help prevent cardiovascular disease, and that poor sleep can help doctors identify who might be at risk of the condition.
Doctors have long known that sleep influences factors that affect the heart, such as diet and physical activity. You’re more likely to crave junk food when you’re sleep-deprived, and motivating yourself to exercise is harder when you’re tired. Now more research suggests that sleep also has a direct effect on heart health.
If you don’t get enough uninterrupted sleep, you are more at risk of developing hypertension, Type 2 diabetes and obesity, according to Michael Grandner, an associate professor in the department of psychiatry at the University of Arizona College of Medicine and director of its sleep research and behavioral medicine programs, citing several large longitudinal studies.
An understanding of what happens to our bodies during sleep helps explain its role in heart health.
A good night’s sleep helps restore the body’s circadian rhythms, control inflammation, and maintain healthy hormone levels and metabolism, says Dr. St-Onge.
During healthy sleep, our bodies are in a “parasympathetic” state in which the nervous system quiets down to conserve energy and regulate bodily functions. Sleep gives the body a reprieve from a daytime “sympathetic” state, in which our nervous system is girded for activity or meeting a threat. During sleep, heart rate and blood pressure fall and other physiological changes take place that can benefit the heart, scientists are finding.
Normally, a person’s blood pressure is expected to fall at night by 10% or more from daytime levels, a change that scientists call the “nocturnal dip.”
The dip appears to help keep blood pressure lower during the day. Scientists have found that blood pressure in people who get only five or six hours of sleep a night don’t experience the dip. Those less-rested people have higher daytime blood pressure and cardiovascular risk that some scientists say is likely because of increased sympathetic nervous system activity and a rise in stress hormones.
In a study of nearly 4,000 middle-aged men and women, researchers found more atherosclerosis, a condition characterized by a buildup of fatty plaques in the arteries, in people who slept fewer than six hours a night than in those who got seven to eight hours. The scientists found increased amounts of plaque and in more locations in the participants whose sleep was most fragmented compared with other study participants.
Imaging techniques allowed researchers to locate the signs of artery disease before it would become evident to doctors, according to the research, which was published in 2019 in the Journal of the American College of Cardiology.
Interruptions during sleep matter too. Poor quality sleep interferes with the body’s normal rest and repair cycles, scientists believe, disrupting its ability to manage inflammation, the body’s natural immune response to injury that is damaging if it becomes chronic. That appears to be true even in people who think they’re getting enough sleep, according to research by a group of scientists at Columbia University.
The scientists found inflammation—an early warning sign of cardiovascular disease—in blood samples taken from 26 women who were young, healthy and reported they were getting seven to nine hours of sleep a night.
Yet the women were experiencing sleep interruptions, according to the group’s research published in 2018 in the Journal of the American Heart Association. The scientists said the inflammation was likely caused by nighttime sympathetic nerve system activity that stimulates the release of stress hormones.
Scientists are also studying the ways in which sleep may affect how we respond to medical treatments. A review published last month in the Yale Journal of Biology and Medicine found evidence suggesting that a good night’s sleep can make vaccines more effective. And research suggests poor sleep can make cancer treatments less effective, according to a review published in April in the journal Frontiers in Neuroscience.
“Sleep systematically removes you from the external environment to allow your body to do things it can’t do as efficiently when it’s plugged into the world,” says Dr. Grandner.
This article was written by Betsy Morris and published in Barron’s on July 18, 2022.
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