All of our repair processes are happening when we're sleeping, whether that's repairing damage to our DNA to prevent us from getting cancer-causing mutations... Whether we're repairing our brain, so we're cleaning out a lot of gunk that builds up in our brain throughout the day ... When we sleep, it's like we clean that all out ... It's very important for preventing the build-up of protein aggregates, like amyloid-beta, which is involved in Alzheimer's disease...