News / Health

Sleep Cleanses Brain of Waste, Study Says

Study Shows Sleep Helps Keep Brains Healthyi
October 21, 2013 10:19 PM
Why do we need sleep? Scientists have found a possible answer to this age-old question. And, as VOA's Carol Pearson reports, the answer may lead to new treatments for neurological disorders such as Alzheimer's or Parkinson's disease.
Related report by Carol Pearson

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While we’re asleep, our brains are doing more than recharging for the next day.  They’re also tidying up, using a cleaning process scientists hope could lead to treatments for ‘dirty brain’ diseases like Alzheimer’s.

Sleep can flush toxins from the brain that accumulate during the course of the day according to a study which may change understanding about the biological purpose of sleep.

“This study shows that the brain has different functional states when asleep and when awake,” said Maiken Nedergaard, M.D., D.M.Sc., co-director of the University of Rochester Medical Center (URMC) Center for Translational Neuromedicine and lead author of the article. “In fact, the restorative nature of sleep appears to be the result of the active clearance of the by-products of neural activity that accumulate during wakefulness.”

Researchers said the study revealed that the brain’s unique method of waste removal – dubbed the glymphatic system – is highly active during sleep, clearing away toxins responsible for Alzheimer’s disease and other neurological disorders. Furthermore, the researchers found that during sleep the brain’s cells reduce in size, allowing waste to be removed more effectively.

Since the lymphatic system, which is responsible for disposing cellular waste from the rest of the body, does not extend to the brain, scientists had long puzzled about how the brain cleaned itself.

Using two-photon miscroscopy to study mice brains, the researchers discovered what they call a “plumbing system that “piggybacks” on the brain’s blood vessels and pumps cerebral spinal fluid (CSF) through the brain’s tissue, flushing waste back into the circulatory system and onto the liver for filtering.

The accumulation of waste in the brain can lead to diseases such as Alzheimer’s disease.

The researchers said that since pumping CSF demands a great deal of energy, it might perhaps be better to do it when the brain is not occupied with processing information during waking hours

“The brain only has limited energy at its disposal and it appears that it must choice between two different functional states – awake and aware or asleep and cleaning up,” said Nedergaard. “You can think of it like having a house party. You can either entertain the guests or clean up the house, but you can’t really do both at the same time.”

Researchers also found that cells in the brain “shrink” by 60 percent during sleep. They said the contraction allows more space between the cells, which allows the CSF to flow through more freely.

“These findings have significant implications for treating ‘dirty brain’ disease like Alzheimer’s,” said Nedergaard. “Understanding precisely how and when the brain activates the glymphatic system and clears waste is a critical first step in efforts to potentially modulate this system and make it work more efficiently.”

The study was published in the journal Science.

Here's a short video on the findings:

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Comment Sorting
by: PermReader
October 23, 2013 9:19 AM
Other researchers were interested in the intellectual functions of the sleeping brain, so it looked strange - the sleep of the brainless insects.

by: Yoshi from: Sapporo
October 21, 2013 4:48 AM
Interesting story! We spend almost one third of the whole life span in sleep so that it has good reason anyone is interested in the purpose of sleep. It is usual that the older ppl get, the shorter sleeping time becomes. It would be the cause of senile dementia with the accumulation of β-amyloid due to its decreased clearance in brain. Thank you.

by: Onifade, 'Muyiwa from: Nigeria
October 20, 2013 5:47 PM
Really, sleep is very good for healthy condition of the entire body whose brain is the remote control.

by: Ramnarayan from: Florida, USA
October 20, 2013 4:00 PM
This is amaziing. All tissues need a cleaning/ detoxification mechanism. For the brain it has been a challenge to document this. The current generation science and technology seems to hold lot of clues to life. As a scientist and an educator, I am thrilled to see VOA actively put such stories in the limelight.
Contrary to to an another writter, this is not a sham. To take such an attitutde over a scientific discovery is crude. Let us look at this observation for what it is; the secrets of brain untangled.

by: jam from: snapper
October 18, 2013 6:01 PM
Purge the waste from TV. Movies. video games. newspapers. Hollywood trash.rap music and politics.

by: Dr. Barry Marr from: USa
October 18, 2013 4:18 PM
As long as our so-called "government" is putting FLUORIDE in the tap water, and MERCURY in all the vaccines, and GMO in the foods, one only needs to read the comment in the article re how "pollution causes cancer" to know that, this article is a sham, and that cancer and cognitive disorders are manufactured by our own government eugenics monsters. Time to wake up people.

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