Sleep is such a waste of time, but we need it. If we don't, we'll die. We've understood the negative effects associated with the lack of sleep but no one really knew why we needed it. Up until now.

The scientists at the University of Rochester have found out the reason why our brain needs sleep to survive. When we sleep, our brain takes the time to clean out the build-up of brain junk we accumulate during waking hours.

Cells produce a lot of waste product on a daily basis, and the rest of the body has this waste cleared out by the lymphatic system. The brain is disconnected from that, so it needs another way to do that clean up. So when we sleep, the brain employs its own garbage men via cerebrospinal fluid.

They move twice as fast as you're sleeping because your neurons shrink by half, making the fluid channels wider.

“This study shows that the brain has different functional states when asleep and when awake,” said UR researcher Maiken Nedergaard. “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.”

In other words, get lots of sleep. You need it more than you think.

[Science Mag, Eureka Alert Image: Flickr, Planet Chopstick]