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Sleeplessness and Circadian Rhythm Disorder

What Is a Biological Clock (Circadian Rhythm)? What Are Biological Clock Sleep Disorders?

Patient Comments
  • 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.
  • Symptoms of a biological sleep disorder include:
    • Poor concentration
    • Depression
    • Difficulty concentrating
    • Daytime sleepiness
    • Problems falling asleep and staying asleep
    • Problems with school or work performance
    • Decreased cognitive skills
    • Headaches
    • Problems with coordination
    • Digestive problems
  • The malfunctioning of a person's circadian system, or biological clock, causes circadian rhythm disorders.
  • Sleep-wake cycle is a type of circadian rhythm disorder and can be categorized into two main groups, transient disorders (short-term) and chronic disorders.
  • Examples of transient disorders that cause biological clock disorders include jet lag, altered sleep schedule due to work hours or social responsibilities, and illness.
  • Irregular sleep-wake cycle, delayed sleep-phase syndrome (DSPS), and advanced sleep-phase syndrome (ASPS) are examples of chronic biological clock disorders.
  • Advanced sleep-phase syndrome 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).
  • 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. This is most common in individuals in nursing homes and other environments lacking in time cues.
  • DSPS is characterized by a persistent (that is, lasting longer than 6 months) inability to fall asleep and awaken at socially acceptable times. People 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). This disorder is more common in teens and young adults than in older people.
  • 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.
  • ASPS occurs less frequently than DSPS and is most commonly seen in the elderly and in individuals’ who are depressed.
  • Total sleep time is normal in individuals with ASPS, DSPS, and an irregular sleep-wake schedule.
  • Daily sleep logs demonstrate irregularity not only of sleep, but also of daytime activities, including eating and other things that may disrupt the person’s biological clock.
Medically Reviewed by a Doctor on 11/20/2017
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Types of Sleep Disorders

Disruptive sleep-related problems are called parasomnias. The two main types of parasomnias are primary and secondary. Types of secondary parasomnias include seizures, arrhythmias, and GERD.


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