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Dr. Michael Breus, Ph.D., a board-certified sleep specialist in Los Angeles, first introduced the four chronotypes based on sleep-wake patterns seen in certain animals.
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]
Bimodal sleep in humans was more common before the Industrial Revolution. [36] Different characteristic sleep patterns, such as the familiarly so-called "early bird" and "night owl", are called chronotypes. Genetics and sex have some influence on chronotype, but so do habits. Chronotype is also liable to change over the course of a person's ...
This pattern was common in preindustrial societies, and it was most common to sleep early ("first sleep"), wake around midnight, and return to bed later ("second sleep"). [10] Along with a nap in the day, it has been argued that this is the natural pattern of human sleep in long winter nights.
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Among mammals, infants sleep the longest. [44] Human babies have 8 hours of REM sleep and 8 hours of NREM sleep on an average. The percentage of time spent on each mode of sleep varies greatly in the first few weeks of development and some studies have correlated this to the degree of precociality of the child. [45]
Familial natural short sleep is a rare, genetic, typically inherited trait where an individual sleeps for fewer hours than average without suffering from daytime sleepiness or other consequences of sleep deprivation. This process is entirely natural in this kind of individual, and it is caused by certain genetic mutations.
Familial sleep traits are heritable variations in sleep patterns, resulting in abnormal sleep-wake times and/or abnormal sleep length. Circadian rhythms are coordinated physiological and biological changes that oscillate on an approximately 24-hour cycle.