Why do we need to sleep about a third of our lives away? Isn’t it annoying to have to waste time sleeping when we have so many important things we would like to be doing?
We already know that getting too little sleep for several nights in a row can have serious consequences for our health.
Now a new study has come up with an idea as to why we need to spend so much time sleeping: In the hours spent slumbering, the brain is hard at work removing toxins produced during our waking hours.
A Biological Dishwasher
Through a series of experiments on mice, the researchers showed that during sleep, cerebral spinal fluid is pumped around the brain and flushes out waste products like a biological dishwasher. (Editor’s note: Care2 does not endorse animal testing and believes there are viable alternatives to medical research that do not involve the testing or killing of animals.)
The process helps to flush out the molecular detritus that brain cells produce as part of their natural activity, along with toxic proteins that can lead to dementia when they build up in the brain, the researchers say.
Maiken Nedergaard, who led the study at the University of Rochester, N.Y., said the discovery might explain why sleep is crucial for all living organisms.
Writing in the journal Science, Nedergaard describes how brain cells in mice shrank when they slept, making the space between them on average 60 percent greater. This made the cerebral spinal fluid in the animals’ brains flow ten times faster than when the mice were awake.
As NPR explains:
The process is important because what’s getting washed away during sleep are waste proteins that are toxic to brain cells, Nedergaard says. This could explain why we don’t think clearly after a sleepless night and why a prolonged lack of sleep can actually kill an animal or a person, she says.
So why doesn’t the brain do this sort of housekeeping all the time? Nedergaard thinks it’s because cleaning takes a lot of energy. “It’s probably not possible for the brain to both clean itself and at the same time [be] aware of the surroundings and talk and move and so on,” she says.
A New Approach to Alzheimer‘s
Even though the brain-cleaning process has only been observed in mice, rats and baboons, and not yet in humans, Nedergaard is hopeful that it could offer a new way of understanding human brain diseases including Alzheimer’s. That’s because one of the waste products removed from the brain during sleep is beta amyloid, the substance that forms sticky plaques associated with Alzheimer’s.
Nedergard also believes that her work could pave the way for medicines that slow the onset of dementia caused by the build-up of waste in the brain.
However, not everyone is in complete agreement about this new theory.
Jim Horne, professor emeritus and director of the sleep research centre at the U.K.’s Loughborough University, is one of several detractors. Horne warns that what happens in the fairly simple brain of a mouse could be very different to what happens in the far more complex human brain.
There are clearly many more questions to ask, and time will tell whether the same brain-cleaning system that works in mice is also applicable to humans.
Meanwhile, I think we can all agree that it is wonderful to wake up feeling refreshed after a good night’s sleep, so perhaps there is something in this new theory.
Now I would like to know if this research can help those of us who are persistent insomniacs get a better night’s sleep.
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