If you toss and turn at night or rattle the windows with your snores, you may be headed for heart trouble.
Sleep, Shakespeare knew, is the chief nourisher in life’s feast. Without restful sleep, your heart health deteriorates.
“Well-run observational studies have connected poor sleep with poor cardiovascular outcomes and identified the pathways through which the damage occurs. However, we need further research to understand the impact of improving sleep on lowering this risk,” says Dr. Susan Redline, the Peter C. Farrell Professor of Sleep Medicine at Harvard Medical School.
Poor sleep affects the heart
Insomnia is the best-known sleep problem. People with insomnia have trouble falling asleep or staying asleep.
But a different kind of disturbed sleep—sleep apnea—has an even more profound effect on the heart. During sleep apnea the back of the throat relaxes, cutting off oxygen. Sleep apnea sufferers actually stop breathing from 15 to more than 100 times an hour. Each pause causes oxygen levels to drop, making it hard for the heart to do its job of pumping oxygen-rich blood through the arteries.
Sleep problems affect the heart in several ways. Blood pressure normally drops during sleep. But in people with sleep disorders, blood pressure typically does not drop and may even rise at night. After several nights, blood pressure may remain elevated around the clock. Over time, high blood pressure damages the lining of the blood vessels, creates inflammation, and predisposes the arteries to developing atherosclerosis.
Inadequate sleep and poor quality sleep also cause levels of the stress hormone cortisol to rise. High cortisol levels and systemic inflammation can trigger or worsen insulin resistance, setting the stage for diabetes as well as for heart disease.
“Sleeping less than four or five hours a night for three or four nights has measurable effects on insulin and cortisol levels. We don’t know how long this must continue before this increases the risk of heart attack or stroke,” says Dr. Redline, of Harvard-affiliated Brigham and Women’s Hospital.
Snoring, a symptom of sleep apnea, is a risk factor all its own. Snoring causes vibratory stress in the neck that can damage the carotid arteries and lead to stroke.
Questions to ask your doctor about: Sleep
Treatment may not lower risk
Whether restoring peaceful sleep lowers heart risk is unclear.
“There is a lot of work to be done to understand the health impact of treating sleep disorders,” says Dr. Redline. “There is some evidence that treating sleep apnea with continuous positive airway pressure [CPAP] or an oral appliance to improve breathing during sleep may improve blood pressure at night. But we don’t yet have the rigorous research needed to tell us when therapy should be started or what is the best therapy for an individual.”
These unanswered questions are fertile ground for study. Specialists at the Division of Sleep Medicine at Harvard Medical School are hoping to fill the information gaps through research. One active trial, funded by the National Institutes of Health, is testing four different treatment strategies on people with sleep apnea and cardiovascular risk factors, with the aim of assessing treatment effects on 24-hour blood pressure. Another study is comparing bariatric surgery with CPAP in overweight people with sleep apnea. Results—and possible new avenues for preventing cardiovascular events—are expected next year.