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Circadian rhythm sleep disorders are a family of sleep disorders affecting the timing of sleep. People with circadian rhythm sleep disorders are unable to sleep and wake at the times required for normal work, school, and social needs. They are generally able to get enough sleep if allowed to sleep and wake at the times dictated by their body clocks. Unless they have another sleep disorder, their sleep is of normal quality. Humans have biological rhythms, known as circadian rhythms, which are controlled by a biological clock and work on a daily time scale. Due to the circadian clock, sleepiness does not continuously increase as time passes. Instead, the drive for sleep follows a cycle, and the body is ready for sleep and for wakefulness at different times of the day.
Types of circadian rhythm sleep disorders The circadian rhythm sleep disorders are: Normal circadian rhythms Among people with healthy circadian clocks, there are "larks" or "morning people" who prefer to sleep and wake early, and there are "owls" who prefer to sleep and wake at late times. Whether they are larks or owls, people with normal circadian systems: Researchers have placed volunteers in caves or special apartments for several weeks without clocks or other time cues. Without time cues, the volunteers tended to go to bed an hour later and to get up about an hour later each day. These experiments appeared to demonstrate that the "free-running" circadian rhythm in humans was about 25 hours long. However, these volunteers were allowed to control artificial lighting and the light in the evening caused a phase delay. More recent research shows that adults of all ages free-run at an average of 24 hours and 11 minutes. To maintain a 24 hour day/night cycle, the biological clock needs regular environmental time cues, e.g. sunrise, sunset, and daily routine. Time cues keep the normal human circadian clock aligned with the rest of the world. Circadian rhythm abnormalities Persistent circadian rhythm sleep disorders such as Non-24 hour sleep-wake syndrome are believed to be caused by a reduced ability to reset the sleep/wake cycle in response to environmental time cues. For example, these individuals' circadian clocks might have an unusually long cycle, or might not be sensitive enough to time cues. People with DSPS, which is more common, do entrain to nature's 24 hours, but are unable to sleep and awaken at socially acceptable times, sleeping instead, for example, from 4 a.m. to noon. See also | |||||||||||||||
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