What Level of Sleep is Best for Brain Health?

November 15, 2023

Getting plenty of deep sleep as we age may be critical for brain health, according to a new report. The study found that in older men and women, as little as a 1 percent decrease in the amount of time spent in deep sleep each night translates to a 27 percent increase in the risk of dementia. 

The findings add to growing evidence that sound sleep is critical for the health of the brain. “Slow-wave sleep, or deep sleep, supports the aging brain in many ways, and we know that sleep augments the clearance of metabolic waste from the brain, including facilitating the clearance of proteins that aggregate in Alzheimer’s disease,” said study author Matthew Pase, an associate professor of psychology and neurology at Monash University in Australia. 

For the study, published in JAMA Neurology, Dr. Pase and his colleagues studied 346 men and women older than 60. All were part of the Framingham Heart Study, a long-running, multi-generational study examining lifestyle and health risks among families originally living in Massachusetts. 

Study participants underwent two studies in a sleep lab, between 1995 to 1998, and again between 2001 and 2003. The sleep studies measured their typical sleep patterns, including how much time they spent in the various stages of sleep. Deep sleep, or non-REM slow-wave sleep, is the third stage of sleep and is thought to be particularly critical for brain health. During this time, harmful substances are thought to be cleared from the brain, including toxic forms of beta-amyloid, the protein that builds up in the brains of those with Alzheimer’s disease. Deep sleep is also considered a good marker of overall sleep quality.  

Over the next 17 years, researchers followed the participants and assessed them for signs of dementia. During this time, 52 had been given a diagnosis of Alzheimer’s disease or other forms of dementia. 

On average, the amount of time that people spent in deep sleep decreased slightly as people grew older. The rate of decline in slow-wave sleep loss accelerated after age 60, peaked between the ages 75 to 80, and then slowed. 

But those with the greatest declines in slow-wave sleep had the highest risk of developing dementia. Each 1 percent decline in slow-wave sleep was tied to a 27 percent increased risk of any form of dementia, and a 32 percent increased risk of developing Alzheimer’s disease.  

The researchers considered other conditions that can affect dementia risk, including advancing age, genetics, whether someone smoked, or the use of sleeping pills or antidepressant drugs. However, the increased risk of dementia with less time spent in deep sleep was independent of these traits.

“Our findings suggest that slow wave sleep loss may be a modifiable dementia risk factor,” said Dr. Pase. 

The researchers also found that those who had an increased genetic risk for Alzheimer’s disease also showed the greatest declines in slow-wave sleep. It is possible that changes to the brain in those prone to Alzheimer’s disease may itself set up a kind of vicious cycle in which accumulating beta-amyloid impairs deep sleep as we age, further weakening the brain. 

Regardless of the underlying causes, the findings build on growing evidence that deep slumber may help guard against memory loss and the ravages of Alzheimer’s disease. A study in May, for example, found that in people who had high levels of beta-amyloid in the brain, those who got a lot of sound, deep sleep during the night performed better on memory tests than those who slept worse and did not get a lot of deep sleep. Deep sleep seemed to provide a compensatory boost against the negative effects of beta-amyloid on the brain, consistent with other studies that have shown the more soundly we sleep, the less buildup in the brain of beta-amyloid.  

Sleep problems generally increase with advancing age and, as these and other studies show, may be priming the brain for dementia. While many people turn to sleeping pills, these drugs do not fully induce deep sleep, and may in fact increase the risk of developing Alzheimer’s disease. There may be safer, more effective and longer lasting natural remedies for a good night’s sleep.  

  • Consider psychological approaches like cognitive behavioral therapy, or CBT, which experts now recommend as the first-line treatment for sleep problems. CBT teaches people to challenge negative or stressful thoughts at bedtime with positive thoughts that induce relaxation. Before going to bed, think of soothing images or try meditation to help clear your head of anxious thoughts. 
  • Avoid coffee and other caffeine-rich beverages after 3 p.m. Avoid alcohol in the hours before bedtime. 
  • Practice good sleep hygiene. Try to keep a consistent sleep schedule, going to bed around the same time each night. Keep the bed a place to sleep, rather than watching TV. If you can’t fall asleep within about 20 minutes, get out of bed and pursue a soothing activity like taking a bath, listening to music or reading. But avoid phones, e-readers (like the Kindle) and computer tablets near bedtime. The light they emit can interfere with our natural body rhythms.

Until more effective treatments or a cure for Alzheimer’s disease are found, getting better quality sleep may be one more way to help slow the onset of dementia as the years advance.  

By ALZinfo.org, The Alzheimer’s Information Site. Reviewed by Eric Schmidt, Ph.D., Fisher Center for Alzheimer’s Research Foundation at The Rockefeller University. 

Source: Jayandra J. Himali, PhD; Andree-Ann Baril, PhD; Marina G. Cavuoto, PhD; et al: “Association Between Slow-Wave Sleep Loss and Incident Dementia.” JAMA Neurology, October 30, 2023. 


Alzheimer's Articles