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Sleeplessness and Circadian Rhythm Disorder

What are circadian rhythm disorders?

A person's circadian rhythm is an internal biological clock that regulates a variety of biological processes according to an approximate 24-hour period. Most of a person's body systems demonstrate circadian variations. The body systems with the most prominent circadian variations are the sleep-wake cycle, the temperature regulation system, and the endocrine system.

The malfunctioning of a person's circadian system, or biological clock, causes circadian rhythm disorders. The circadian rhythm disorder related to the sleep-wake cycle can be categorized into the following 2 main groups:

  • Transient disorders
    • Jet lag
    • Altered sleep schedule due to work hours or social responsibilities
    • Illness
  • Chronic disorders
    • Delayed sleep-phase syndrome (DSPS)
      • DSPS is characterized by a persistent (that is, lasting longer than 6 months) inability to fall asleep and awaken at socially acceptable times. Individuals with DSPS fall asleep late (for example, in the early morning hours) and wake up late (for example, in the late morning hours or in the early afternoon hours).
      • Once asleep, however, persons with DSPS are able to maintain their sleep and have normal total sleep times. In contrast, persons without DSPS who are unable to sleep because of difficulties initiating and maintaining sleep have a lower than normal total sleep time than persons with DSPS.
    • Advanced sleep-phase syndrome (ASPS)
      • ASPS is characterized by a persistent early evening sleep onset time (between 6:00 pm and 9:00 pm) and an early morning wake-up time (between 3:00 am and 5:00 am).
      • ASPS occurs less frequently than DSPS and is most commonly seen in elderly individuals and in individuals who are depressed.
    • Irregular sleep-wake cycle
      • An irregular sleep-wake schedule features multiple sleep episodes without evidence of recognizable ultradian (a series of shorter biological rhythms occurring within a 24-hour period) or circadian features of sleep and wakefulness.
      • As in persons with ASPS and DSPS, total sleep time is normal in persons with an irregular sleep-wake schedule.
      • Daily sleep logs demonstrate irregularity not only of sleep but also of daytime activities, including eating.
Medically Reviewed by a Doctor on 6/27/2016
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