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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]
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]
Deep sleep refers to slow-wave sleep — a stage in the sleep cycle when brain waves slow down. Getting enough deep sleep is crucial for numerous bodily functions. But how to increase deep sleep ...
In adults, wakefulness increases, especially in later cycles. One study found 3% awake time in the first ninety-minute sleep cycle, 8% in the second, 10% in the third, 12% in the fourth, and 13–14% in the fifth. Most of this awake time occurred shortly after REM sleep. [22]
The minimum amount of sleep recommended for adults by the American Academy of Sleep Medicine is seven hours. ... At night, the body cycles through five stages which fall into two categories: rapid ...
REM sleep typically occupies 20–25% of total sleep in adult humans: about 90–120 minutes of a night's sleep. The first REM episode occurs about 70 minutes after falling asleep. Cycles of about 90 minutes each follow, with each cycle including a larger proportion of REM sleep. [27]
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 ]
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]