What happens during sleep?
Even though we know about the benefits of sleep and the problems that come when we lose sleep, sleep scientists will still tell you that sleep is still a little bit mysterious.
We know that during the first 2 hours of sleep, our brains are working to discharge cellular debris(something the rest of our bodies do by using the lymphatic system).
Sleep comes on gradually in stages. The first stages are light.
About 90 minutes after we fall asleep, we enter the 1st stage of REM(rapid eye movement) sleep. The 1st REM stage is about 10 minutes, but each subsequent cycle lasts longer and the final REM stage may last up to an hour!
In Matthew Walker’s fascinating book “Why We Sleep”, he discusses these two major milestones REM sleep gave us as we evolved:
In between these REM cycles, we enter non-REM sleep, which is when our bodies repair its cells and strengthens its immune system. We need at least 3 of these REM and non-REM cycles every night, but 4 or 5 is better.