Non-rapid eye movement (NREM) sleep is a type of sleep during which dreaming does not occur. In this phase, the electroencephalographic (EEG) recordings display slow, high-voltage brain waves. The sleeper's breathing and heart rate become slow and steady, blood pressure drops, and the body remains mostly still. NREM sleep is divided into four progressively deeper stages.In contrast, rapid eye movement (REM) sleep is the stage associated with dreaming. Typically, we experience 3 to 5 REM cycles each night, occurring every 1 to 2 hours. These periods vary in duration, lasting anywhere from 5 minutes to over an hour. REM sleep is distinguished by rapid, low-voltage brain waves, as well as irregular breathing, heart rate, and occasional muscle twitches.Approximately 80% of our sleep consists of NREM sleep. If you sleep for 7 to 8 hours per night, nearly all of that time, except for about an hour and a half, is spent in the dreamless state of NREM sleep.
