Study: Deep Sleep Best for Brain ‘Cleaning,’ Emphasizes Link Between Sleep and Alzheimer’s

Deep, non-REM sleep is optimal for our brains to wash away waste.

By Claire Hansen, Staff WriterFeb. 27, 2019
By Claire Hansen, Staff WriterFeb. 27, 2019, at 2:00 p.m.
U.S. News & World Report

Study: Deep Sleep Best for Brain ‘Cleaning’

Older woman sleeping in a bed.

Deep sleep helps brains get rid of waste. (Getty Images)

Deep, non-REM sleep helps people's brains to wash away toxic proteins and waste, a new study found, reinforcing the link between sleep deprivation, aging and Alzheimer's disease.

The study, out Wednesday in the journal "Science Advances," found that the slow and consistent brain activity experienced during deep, non-REM sleep is ideal for the brain's glymphatic system, which effectively "cleans" the brain of toxic proteins like beta amyloid and tau.

Because the build up of proteins in the brain – including tau – have been linked to Alzheimer's disease and dementia, researchers say the study further underscores the link between poor sleep and dementia. It also notes that sleep becomes lighter and more disrupted as people age.

"Sleep is critical to the function of the brain's waste removal system and this study shows that the deeper the sleep the better," said Maiken Nedergaard, co-director of the Center for Translational Neuromedicine at the University of Rochester Medical Center and lead author of the study. "These findings also add to the increasingly clear evidence that quality of sleep or sleep deprivation can predict the onset of Alzheimer's and dementia."

In the study, researchers anesthetized mice with six different drug cocktails and tracked the animals' brain activity, cardiovascular activity and the flow of a "cleaning" fluid through the brain. The drug combination that put the mice in a biological state most similar to the one experienced in deep, non-REM sleep was optimal for brain cleaning, researchers found.

Researchers say the study also demonstrates that the brain's glymphatic system can be manipulated, which points to promising clinical solutions for aging patients and those with poor sleep.

Because the drug cocktails used on the mice resemble anesthesia used by medical professionals on patients, the research further illuminated the cognitive difficulties patients, specifically aging patients, experience when waking up from sedation – and suggests specific drugs that could limit those difficulties.

Claire Hansen, Staff Writer

Claire Hansen is a reporter at U.S. News & World Report. You can follow her on Twitter and emai...  Read moreClaire Hansen is a reporter at U.S. News & World Report. You can follow her on Twitter and email her at



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