Margen
We spend almost a third of our lives asleep, and for a long time it looked like wasted time. It isn't: while you sleep, the brain does a deep clean it can't afford while you're awake and thinking.
By day, mental activity generates waste, small leftover molecules that build up between the neurons. At night something striking happens: the brain's cells shrink a little and leave more space between them. Through those channels flows the fluid that bathes the brain, sweeping the rubbish outward like a tide cleaning the beach.
Among that waste are proteins that, piling up over years, are linked to diseases like Alzheimer's.
So sleeping badly isn't just being tired the next day: it's leaving the rubbish uncollected. Your brain works the night shift, and it's best not to take it away.