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Your Brain Cells Shrink While You Sleep (And That’s a Good Thing)

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In a predatory world, sleep doesn’t make much evolutionary sense. Why would any creature lie down, shut its eyes and not move for about a third of a day? It’s like an invitation to be eaten.

Now a new study out of the University of Rochester Medical Center (URMC) suggests sleep is necessary for the brain to get rid of waste. The study, published in the journal Science, also reveals that the brain’s cells shrivel up by 60% while we sleep to wash away the cellular garbage more effectively. Researchers believe that all the cleaning activity is one of the reasons the brain uses about as much energy while in sleep as while in wake mode. Sleep is known to perform many critical functions, including consolidating memories and recharging cells, but this is the first time it has been linked with cerebral rubbish removal.

The new findings are a continuation of work that Dr. Maiken Nedergaard, the lead author of the current study, published in 2012 in the journal Science Translational Medicine. In that report, she and her colleagues used a new imaging technique, two-photon microscopy, to show that mice brains, which are good models of human brains, have their own plumbing system for disposing of molecular detritus. Known as the glymphatic system, it hitches a ride alongside the brain’s blood vessels to pump cerebrospinal fluid through the brain tissue and wash waste back into the circulatory system, where the liver eventually disposes it.

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The new study, also in mice, suggests that while the body powers down, the glymphatic system ramps up, becoming 10 times more active than when the brain is awake. And because the brain’s cells shrink during sleep, the researchers believe, it’s easier for the fluid to flush out its many corridors. During sleep, proteins that are responsible for Alzheimer’s disease and other neurological disorders are also removed more efficiently from the brain than during waking hours. The body’s chief sanitation worker, the lymphatic system, isn’t sufficient for cleaning out the brain because of the brain-blood barrier, the body’s equivalent of a picket line, which prevents certain cleansing agents from passing through the blood and into the brain. But the glymphatic system, composed of cerebrospinal fluid, is given a special pass into the brain, and can pull out toxins and other waste products, primarily during sleep.

The findings raise interesting questions about how sleep may affect the progression of Alzheimer’s or other neurogenerative disorders, but they also provide a strong warning for anybody who skips sleep. The short version: don’t.

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“The brain only has limited energy at its disposal and it appears that it must choose between two different functional states – awake and aware or asleep and cleaning up,” said Nedergaard, a co-director of the URMC Center for Translational Neuromedicine, in a statement. “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.” And you can’t do either one without the other for long.

11 comments
JimYoung1
JimYoung1

Sitting upright in a wheelchair for days on end, rather than proper sleep position has led to Deep Vein Thrombosis. I've spent time in hospitals having Vena Cava filters implanted to hopefully prevent the blood clots from reaching the lungs, heart, brain, etc.. Due to frequent falls when I try to walk (assisted with a cane), the Hematologists decided on the filters rather than blood thinners. As they explained it; one wrong fall, medicated with blood thinners could cause fatal bleeding in the brain since I usually end up on my head or face, (not to mention the difficulty of getting up from the floor, lol). Gotta raise my legs above my heart to reduce the swelling of lower extremities frequently. Retirement is not what I expected but gotta deal with it day by day...

JimYoung1
JimYoung1

Certain health issues disrupt my sleep pattern. I often go a couple of days without 'normal sleep', rather a brief nodding out when it seems too difficult to transfer from wheelchair to my hospital bed. I get myself into trouble speaking truth to people who have done me wrong. I try to prevent the controversy that arises when I speak the truth that is on my mind at times. Enough stress to deal with, considering my own health issues without having to deal with others real or perceived difficulties. Some friends and family members expect too much from me and I always try to help, often in bad judgment...


MariamMidhat
MariamMidhat

the research is very nice , but its written that we dont have to sleep for long period because this will affect negatively and no removing of the toxins, and also not to sleep for short period as there willn't be effect, then whats the range of hours the person should sleep

BudgetDoc
BudgetDoc

It's still tempting to go on the "DaVinci Style" sleep schedule and forgo real sleep in favor of a few short naps throughout the day, or as my brother likes to say, "I'll sleep when I'm dead".  Nice to be reminded that there's probably a good reason for feeling sleepy.

DrJudi
DrJudi

A counterexample to this theory is that of the Haredi Jews who consider sleep a waste of time, and they spend long hours five and a half days a week studying. Most of them live long lives with no apparent decrease in their cognitive faculties.

robertholt72
robertholt72

Sounds like intelligent design to me.  "Does he who fashioned the ear not hear? Does he who formed the eye not see?"  Psalm 94:9.

AbrahamYeshuratnam
AbrahamYeshuratnam

Pavlov has proved that by keeping a man awake, his fatigued brain will make him  blurt out the truth. Soviet Union's KGB interrogated several suspects by keeping them awake facing a bright light. Sleep is necessary not merely to shrink brain cells but also to store confidential matters without leaking to others.

JohnLong
JohnLong

So that explains why I want to sleep so much after a night of binge drinking. My brain has to flush the bad stuff out. Makes sense.

JimYoung1
JimYoung1

I don't fully agree with that theory since blood thinners do not actually 'thin' the blood. They can reduce the possibility of further clotting as I understand it but it is much too complicated for my feeble brain to comprehend. Perhaps I have been mislead, My knowledge of medical science is limited to what I study. Everything we read on the internet is right; Right? Dead wrong in some cases.

JimYoung1
JimYoung1

@DrJudi  I frequently do the same and except for a brief 'nodding out' I go without what is considered normal sleep for days at a time, and yes my time is spent with constant study. It does though result in bad judgment sometimes and with other issues the lack of elevating my legs above my heart a couple of times a week my legs and feet swell up like balloons. I'm wheelchair bound, partially paralyzed and very little movement has resulted in or contributed to DVT, requiring surgical implantation of vena cava filters to lessen the risk of clots reaching vital organs. What works for some does not always work for all of us...   

JimYoung1
JimYoung1

@AbrahamYeshuratnam  Explains a lot of why I say things I normally curb, when speaking to people who have done me wrong. I am speaking the truth of my thoughts out loud rather than holding it in as I often do to lessen the controversy when the truth is spoken.