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The sleep cycle is an oscillation between the slow-wave and REM (paradoxical) phases of sleep. It is sometimes called the ultradian sleep cycle, sleep–dream cycle, or REM-NREM cycle, to distinguish it from the circadian alternation between sleep and wakefulness. In humans, this cycle takes 70 to 110 minutes (90 ± 20 minutes). [1]
Polyphasic sleep is the practice of sleeping during multiple periods over the course of 24 hours, in contrast to monophasic sleep, which is one period of sleep within 24 hours. Biphasic (or diphasic , bifurcated , or bimodal ) sleep refers to two periods, while polyphasic usually means more than two. [ 1 ]
The sleep cycle of alternate NREM and REM sleep takes an average of 90 minutes, occurring 4–6 times in a good night's sleep. [17] [22] The American Academy of Sleep Medicine (AASM) divides NREM into three stages: N1, N2, and N3, the last of which is also called delta sleep or slow-wave sleep. [23]
Most people get around 1.5 to two hours of slow-wave sleep if they get eight hours of shut-eye. This stage is key to waking up refreshed and ready for the day — and it’s what you’re hoping ...
Within a few months of postnatal development, there is a marked reduction in percentage of hours spent in REM sleep. By the time the child becomes an adult, he spends about 6–7 hours in NREM sleep and only about an hour in REM sleep. [46] [47] This is true not only of humans, but of many animals dependent on their parents for food. [48]
Slow-wave sleep (SWS), often referred to as deep sleep, is the third stage of non-rapid eye movement sleep (NREM), where electroencephalography activity is characterised by slow delta waves. [2] Slow-wave sleep usually lasts between 70 and 90 minutes, taking place during the first hours of the night. [3]
Chronic sleep deprivation (less than 8 hours of sleep) is associated with an increase in body mass index (BMI) and obesity. In a study with 3000 patients, it was found that men and women who sleep less than 5 hours have elevated body mass index (BMI). In another study that followed about 70.000 women for 16 years, there was a significant ...
Cycles of REM and non-REM stages make up sleep. A normal healthy adult requires 7–9 hours of sleep per night. The number of hours of sleep is variable, however the proportion of sleep spent in a particular stage remains mostly consistent; healthy adults normally spend 20–25% of their sleep in REM sleep. [5]