Q & A Library

Print this page | Sign up for free e-bulletins
 | Bookmark This Page

Does Sleep Sweep the Brain?

What happens in the brain while we sleep? I've heard that some sort of cleansing process goes on that protects against Alzheimer's disease. But I've also heard that brain cells shrink while we sleep. Which is right?

Answer (Published 12/27/2013)

Actually, both are right. Some fascinating new research suggests that brain cells do shrink temporarily – increasing the space in between the cells by about 60 percent during sleep, and that this shrinkage has an important purpose. It makes possible a process of "trash removal" that eliminates toxic waste products, including some of the proteins associated with Alzheimer's disease (AD) and other neurological disorders. Studies in mice at the University of Rochester first revealed this waste removal process. The results are significant because the mouse brain is considered a good model of the human brain. The same waste removal system has been seen in the brains of rats and baboons, but so far, not in humans. Once swept out of the brain, the wastes are flushed through the circulatory system into the liver, which renders them harmless.

Related Weil Products
Dr. Weil's Vitamin Advisor for Your Whole Body - Foods, herbs and drugs can all interact, sometimes in unexpected ways. Dr. Weil's Vitamin Advisor takes known interactions into account when developing nutritional supplement recommendations, to help safeguard against adverse effects. Learn more, and get your free, personalized Dr. Weil's Vitamin Advisor recommendation today.

The human lymphatic system is responsible for cleaning wastes out the rest of the body, but it can't penetrate the brain-blood barrier. In their mouse studies, the Rochester investigators found that another network, which they call the "glymphatic" system, takes care of cleaning up the brain. The "g" in "glymphatic" stands for glial cells, which have been called the "glue of the nervous system" because they help hold neurons in place.

The Rochester researchers saw that while the mice they studied were asleep, the nervous system was speedily pumping fluid into the brain and rinsing it out very quickly. Then they discovered that this laundering process was made possible by the shrinkage of brain cells during sleep, a change that allows the fluid to circulate more freely. The brain cells enlarge again when the mice wake up.

Researchers have speculated that the cleansing process can't occur while we're awake because the brain is too busy with other things. They have noted that diseases linked to dementia, including AD, are associated with sleep disorders and that amounts of beta amyloid, the substance that forms the sticky plaques associated with AD, increase while we're awake but decline when we're sleeping.

This cleansing process may explain why sleep is so important to good health. One of the Rochester researchers was quoted in news reports as saying that the trash collection in the brain might explain why our thinking is so foggy when we're deprived of sleep and why prolonged sleeplessness can be lethal in animals and humans.

Conceivably, further investigation of this cleaning process may demonstrate that optimizing sleep can help prevent Alzheimer's by allowing beta amyloid to be swept away more efficiently.

Andrew Weil, M.D.

Creative Commons License Some Rights Reserved Creative Commons Copyright Notice
A portion of the original material created by Weil Lifestyle on (specifically, all question and answer-type articles in the Dr. Weil Q&A Library) is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 United States License.

The Weil Vitamin Advisor
Get your FREE personalized vitamin recommendation & supplement plan today!

Dr. Weil on Healthy Aging
Your Online Guide to the Anti-Inflammatory Diet. Start eating for your health - begin your free trial now.

Dr. Weil's Spontaneous Happiness
Achieve emotional well-being in just eight weeks! Start your 10-day free trial now!

Vitamin Library
Supplement your knowledge with Dr. Weil's essential vitamin facts. Learn why they are necessary and more.

Dr. Weil's Optimum Health Plan
Your 8-week plan to wellness.
Begin your journey today!

Dr. Weil's Head-to-Toe Wellness Guide
Your guide to natural health.
Use the Wellness Guide today!

Dr. Weil's Anti-Inflammatory Diet
Food Pyramid

Our interactive tool can help improve overall health through diet.

Condition Care Guide
Learn about health conditions from acne to vertigo, and Dr. Weil's view of the best treatment options for each.

Healthy Recipes
Discover a treasure trove of healthy, healing foods and creative, delicious ways to prepare them.

Q&A Library
Over 2,000 questions from you and their corresponding answers from Dr. Weil.

Copyright © 2015 Weil Lifestyle
Information on this web site is provided for informational purposes only and is not intended as a substitute for the advice provided by your physician or other healthcare professional. You should not use the information on this web site for diagnosing or treating a health problem or disease, or prescribing any medication or other treatment.

Ad Choice
Advertising Notice

This Site and third parties who place advertisements on this Site may collect and use information about your visits to this Site and other websites in order to provide advertisements about goods and services of interest to you. If you would like to obtain more information about these advertising practices and to make choices about online behavioral advertising, please click here