Looking in on a sleep study, you’ll see that the brain is actually very active during sleep, cycling through non-REM (NREM) stages and ending in REM sleep approximately five times during the night. Transitions between stages are clearly visible as shifts in EEG patterns.
Graphs illustrating the human sleep cycle typically present an 8-hour time span, as shown here. But this doesn’t tell the whole story of sleep. The amount of time spent sleeping and the content of our sleep changes across the life span. And while a normal night’s sleep lasts approximately 7 hours for a healthy young adult, 30% of working adults get 6 hours or fewer of sleep per night (Centers for Disease Control and Prevention, 2012f).