Research reveals how neurons help “flush” waste during sleep — offering clues to preventing Alzheimer’s and other neurological diseases. 

Sleep is a time to rest, but inside your brain, it’s anything but quiet. While you drift off, your brain shifts into high gear — clearing out waste and refreshing itself for another day of thinking, learning and problem-solving.

Global leaders in neuroimmunology research at Washington University School of Medicine in St. Louis have uncovered a fascinating new detail about this process: neurons — the same cells that drive your thoughts and actions — also act as tiny pumps, sweeping away harmful debris while you sleep. If scientists can harness this natural system, it could lead to new ways to prevent Alzheimer’s, Parkinson’s and other neurodegenerative diseases.

Published in Nature (Feb. 28, 2024), the findings reveal how sleep powers the brain’s built-in cleansing system and what that could mean for brain health.

How your brain cleans itself

Think of your brain as a high-powered engine. It burns fuel to function, but that process generates waste — metabolic debris that, if left unchecked, can clog the system. While scientists have long known that sleep plays a key role in flushing out toxins, the mechanics remained a mystery.

The WashU Medicine team discovered that neurons fire in synchronized waves during sleep — like pulses of electricity lighting up the brain. “These neurons are miniature pumps. Synchronized neural activity powers fluid flow and removal of debris from the brain,” explained first author Li-Feng Jiang-Xie, PhD, a postdoctoral research associate in the Department of Pathology & Immunology. “If we can build on this process, there is the possibility of delaying or even preventing neurological diseases, including Alzheimer’s and Parkinson’s disease, in which excess waste — such as metabolic waste and junk proteins — accumulate in the brain and lead to neurodegeneration.”

“We knew that sleep is a time when the brain initiates a cleaning process to flush out waste and toxins it accumulates during wakefulness. But we didn’t know how that happens. These findings might be able to point us toward strategies and potential therapies to speed up the removal of damaging waste and to remove it before it can lead to dire consequences,” explained Jonathan Kipnis, PhD, the Alan A. and Edith L. Wolff Distinguished Professor of Pathology & Immunology and a BJC Investigator. Kipnis is the senior author on the paper.

Brain health: quality over quantity

We’ve all heard that getting eight hours of sleep is critical for health. But what if the key isn’t the number of hours — but how efficiently your brain cleans itself during sleep? “One of the reasons we sleep is to cleanse the brain,” explained Kipnis. “If we can enhance this process, maybe we could improve brain health — especially for people who struggle with sleep.”

This raises intriguing new questions: Are some parts of the brain better at cleaning than others? Could certain sleep cycles be optimized for better waste removal? The team is now exploring these questions, with the hope of unlocking new ways to keep the brain clear, healthy, and protected from disease. Because when it comes to brain health, a good night’s sleep might be the best preventative medicine of all.