More amyloid, less deep sleep; less deep sleep, more amyloid, and so on. We sleep in 90-minute cycles, and it’s only towards the end of each one of these that we go into deep sleep. First, there is NREM sleep (non-rapid eye movement sleep); this is then followed by REM (rapid eye movement) sleep. But you need 90 minutes to get to deep sleep, and one cycle isn’t enough to do all the work. ■ If you drive a car when you have had less than five hours’ sleep, you are 4.3 times more likely to be involved in a crash.

Source: The Guardian September 24, 2017 06:56 UTC