Science: We All Need Sleep to Clean Out Our Brain Garbage

In the persisting mystery of why we sleep, scientists at the University of Rochester have a new theory — we sleep to give our brains time to clean out our literal brain garbage.

Researcher Maiken Nedergaard, who led the sleep study at the University of Rochester, writes in Science, “I think we have discovered why we sleep. We sleep to clean our brains.”

Through their observations on the brains of mice, Nedergaard’s team discovered that during sleep, a cerebral spinal fluid is pumped around the brain to clean out any molecular waste that’s produced by brain cells during their daily activity along with certain toxic proteins that cause lasting damage like dementia.

So why can’t this cerebral spinal fluid be released while we’re awake? Because cleaning your brain takes a fucking lot of work.

From The Guardian:

Nedergaard believes the clean-up process is more active during sleep because it takes too much energy to pump fluid around the brain when awake. “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,” she said in a statement.

According to the scientist, the cerebral spinal fluid flushes the brain’s waste products into what she calls the “glymphatic system” which carries it down through the body and ultimately to the liver where it is broken down.

Another reason this process works better when you’re sleeping than when you’re awake might be because — if what was true for the mice ends up being true for us — the brain cells shrink with sleep and create up to 60% more room for the fluid to flow. And with this extra room, it flows at a rate that’s ten times faster. Pretty cool stuff.

At this point, many scientists are dubious of Nedergaard’s theory, saying that we still don’t know whether or not the process applies to humans. So until anything is proven, we’ll have to settle ourselves with this — sleep is necessary and you could probably use more of it.