Most of all, it’s when you sleep that the brain stores your day’s experiences, primes your memory, and releases hormones that regulate energy, mood, and mental acuity. And the brain completes all this activity is about 7 to 8 hours. Moreover, to understand why it takes so long, it’s necessary to understand how sleep works.
First of all, sleep has two parts: Non Rapid Eye Movement (NREM) sleep and REM sleep. Furthermore, NREM sleep has 3 stages: Stage 1, Stage 2, and Stage 3. Moreover, both NREM and REM sleep together occur in cycles that are repeated every 90 to 110 minutes. For example, one complete cycle would be Stage 1 sleep, followed by Stage 2 sleep, followed by Stage 3 sleep, and finally REM sleep. And, each of these sleep stages can last anywhere from 5 to 15 minutes. Because one complete cycle takes about 90 minutes, the brain does about 5 cycles in 450 minutes or 7.5 hours.
In reality, the first half of the night is essentially NREM sleep where the REM portion is short. And the second half of the night is essentially REM sleep where the NREM stages are short.
Most noteworthy, slow-wave sleep is the deepest phase of NREM sleep. And slow-wave sleep occurs in stage 3. Most of all, dreaming and sleepwalking occurs when the brain is in slow-wave sleep. And slow-wave sleep is important for the brain to consolidate memory. Also slow-wave sleep is the most restorative to your body.
As a result, interruptions in slow-wave sleep are the most damaging to your metabolic health. And these interruptions along with other consequences of sleep deprivation occur when you don’t sleep 8 hours. Moreover, the infographic below provides a graphical view of all the consequences to your body from being sleep deprived.