Circadian rhythm sleep disorder
Encyclopedia
Circadian rhythm sleep disorders are a family of sleep disorders affecting, among other things, 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 also have another sleep disorder, their sleep is of normal quality.
Humans, like most animals and plants, have biological rhythms, known as circadian rhythm
s, which are controlled by a biological clock and work on a daily time scale. These affect body temperature, alertness
, appetite
, hormone
secretion etc. as well as sleep timing. Due to the circadian clock, sleepiness does not continuously increase as time passes. A person's desire and ability to fall asleep is influenced by both the length of time since the person woke from an adequate sleep, and by internal circadian rhythms. Thus, the body is ready for sleep and for wakefulness at different times of the day.
Sleep researcher Yaron Dagan in Israel states that "[t]hese disorders can lead to harmful psychological and functional difficulties and are often misdiagnosed and incorrectly treated due to the fact that doctors are unaware of their existence."
s from "larks
", "morning people", who prefer to sleep and wake early, to "owls
", "evening people" or "night people", 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 or Zeitgeber
s, e.g., sunrise, sunset, and daily routine. Time cues keep the normal human circadian clock aligned with the rest of the world.
, "Altered or disrupted sensitivity to zeitgeber
s is probably the most common cause of circadian rhythm disorder."
As of October 1, 2005, the diagnostic codes for circadian rhythm sleep disorders were changed from the 307-group to the 327-group in the Diagnostic and Statistical Manual of Mental Disorders
, Fourth Edition, Text Revision (DSM-IV-TR). The DSM updated to agree with the International Classification of Diseases (ICD-9). The new codes reflect the moving of these disorders from the Mental Disorders section to the Neurological section in the ICD.
Humans, like most animals and plants, have biological rhythms, known as circadian rhythm
Circadian rhythm
A circadian rhythm, popularly referred to as body clock, is an endogenously driven , roughly 24-hour cycle in biochemical, physiological, or behavioural processes. Circadian rhythms have been widely observed in plants, animals, fungi and cyanobacteria...
s, which are controlled by a biological clock and work on a daily time scale. These affect body temperature, alertness
Alertness
Alertness is the state of paying close and continuous attention, being watchful and prompt to meet danger or emergency, or being quick to perceive and act. It is related to psychology as well as to physiology...
, appetite
Appetite
The appetite is the desire to eat food, felt as hunger. Appetite exists in all higher life-forms, and serves to regulate adequate energy intake to maintain metabolic needs. It is regulated by a close interplay between the digestive tract, adipose tissue and the brain. Decreased desire to eat is...
, hormone
Hormone
A hormone is a chemical released by a cell or a gland in one part of the body that sends out messages that affect cells in other parts of the organism. Only a small amount of hormone is required to alter cell metabolism. In essence, it is a chemical messenger that transports a signal from one...
secretion etc. as well as sleep timing. Due to the circadian clock, sleepiness does not continuously increase as time passes. A person's desire and ability to fall asleep is influenced by both the length of time since the person woke from an adequate sleep, and by internal circadian rhythms. Thus, the body is ready for sleep and for wakefulness at different times of the day.
Sleep researcher Yaron Dagan in Israel states that "[t]hese disorders can lead to harmful psychological and functional difficulties and are often misdiagnosed and incorrectly treated due to the fact that doctors are unaware of their existence."
Extrinsic type
Two of these disorders are extrinsic (from Latin extrinsecus, from without, on the outside) or circumstantial:- Jet lagJet lagJet lag, medically referred to as desynchronosis, is a physiological condition which results from alterations to the body's circadian rhythms; it is classified as one of the circadian rhythm sleep disorders...
, which affects people who travel across several time zones. - Shift work sleep disorderShift work sleep disorderShift work sleep disorder is a circadian rhythm sleep disorder characterized by insomnia and excessive sleepiness affecting people whose work hours are scheduled during the typical sleep period...
, which affects people who work nights or rotating shifts.
Intrinsic type
Four of them are intrinsic (from Latin intrinsecus, on the inside, inwardly), "built-in":- Delayed sleep phase syndromeDelayed sleep phase syndromeDelayed sleep-phase syndrome , also known as delayed sleep-phase disorder or delayed sleep-phase type , is a circadian rhythm sleep disorder, a chronic disorder of the timing of sleep, peak period of alertness, the core body temperature rhythm, hormonal and other daily rhythms, compared to the...
(DSPS), characterized by a much later than normal timing of sleep onset and offset and a period of peak alertness in the middle of the night. - Advanced sleep phase syndromeAdvanced sleep phase syndromeAdvanced sleep phase syndrome , also known as the advanced sleep-phase type of circadian rhythm sleep disorder, is a condition in which patients feel very sleepy and go to bed early in the evening and wake up very early in the morning Advanced sleep phase syndrome (ASPS), also known as the...
(ASPS), characterized by difficulty staying awake in the evening and difficulty staying asleep in the morning. - Non-24-hour sleep-wake syndromeNon-24-hour sleep-wake syndromeNon-24-hour sleep-wake syndrome is a chronic circadian rhythm sleep disorder, classified within Chapter VI, Diseases of the Nervous System, in the ICD-10. It can be defined as "a chronic steady pattern comprising one- to two-hour daily delays in sleep onset and wake times in an individual living...
(Non-24), in which the affected individual's sleep occurs later and later each day, with the period of peak alertness also continuously moving around the clock from day to day. - Irregular sleep-wake rhythmIrregular sleep-wake rhythmIrregular sleep–wake rhythm is a rare form of circadian rhythm sleep disorder. It is characterized by numerous naps throughout the 24-hour period, no main nighttime sleep episode and irregularity from day to day. Sufferers have no pattern of when they are awake or asleep, may have poor quality...
, which presents as sleeping at very irregular times, and usually more than twice per day (waking frequently during the night and taking naps during the day) but with total time asleep typical for the person's age.
Normal circadian rhythms
Among people with healthy circadian clocks, there is a continuum of chronotypeChronotype
Chronotype is an attribute of animals, including human beings, reflecting at what time of the day their physical functions are active, change or reach a certain level...
s from "larks
Lark (person)
Lark is a term used to describe a person who usually gets up early in the morning and goes to bed early in the evening. Other terms are "morning person" and "early bird"....
", "morning people", who prefer to sleep and wake early, to "owls
Night owl (person)
Night owl is a term used to describe a person who tends to stay up until late at night. Another name for a night owl is evening person.The opposite of a night owl is an early bird, a lark as opposed to owl, someone who tends to begin sleeping at a time that is considered early and also wakes early...
", "evening people" or "night people", who prefer to sleep and wake at late times. Whether they are larks or owls, people with normal circadian systems:
- can wake in time for what they need to do in the morning, and fall asleep at night in time to get enough sleep before having to get up.
- can sleep and wake up at the same time every day, if they want to.
- will, after starting a new routine that requires their getting up earlier than usual, start to fall asleep at night earlier within a few days. For example, someone used to sleeping at 1 a.m. and waking up at 9 a.m. begins a new job on a Monday, and must get up at 6 a.m. to get ready for work. By the following Friday, the person has begun to fall asleep at around 10 p.m., and can wake up at 6 a.m. feeling well-rested. This adaptation to earlier sleep/wake times is known as "advancing the sleep phase." Healthy people can advance their sleep phase by about one hour each day.
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 or Zeitgeber
Zeitgeber
Zeitgeber is any exogenous cue that synchronizes an organism's endogenous time-keeping system to the earth's 24-hour light/dark cycle. The strongest zeitgeber, for both plants and animals, is light...
s, 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
Non-24-hour sleep-wake syndrome and other persistent circadian rhythm sleep disorders are believed to be caused by an inadequate ability to reset the sleep/wake cycle in response to environmental time cues. These individuals' circadian clocks might have an unusually long cycle, and/or might not be sensitive enough to time cues. People with DSPS, more common than Non-24, do entrain to nature's 24 hours, but are unable to sleep and awaken at socially preferred times, sleeping instead, for example, from 4 a.m. to noon. According to doctors Cataletto and Hertz at WebMDWebMD
WebMD is an American corporation which provides health information services. It was founded in 1996 by Jim Clark and Pavan Nigam as Healthscape, later Healtheon, and then acquired WebMD in 1999 to form Healtheon/WebMD...
, "Altered or disrupted sensitivity to zeitgeber
Zeitgeber
Zeitgeber is any exogenous cue that synchronizes an organism's endogenous time-keeping system to the earth's 24-hour light/dark cycle. The strongest zeitgeber, for both plants and animals, is light...
s is probably the most common cause of circadian rhythm disorder."
As of October 1, 2005, the diagnostic codes for circadian rhythm sleep disorders were changed from the 307-group to the 327-group in the Diagnostic and Statistical Manual of Mental Disorders
Diagnostic and Statistical Manual of Mental Disorders
The Diagnostic and Statistical Manual of Mental Disorders is published by the American Psychiatric Association and provides a common language and standard criteria for the classification of mental disorders...
, Fourth Edition, Text Revision (DSM-IV-TR). The DSM updated to agree with the International Classification of Diseases (ICD-9). The new codes reflect the moving of these disorders from the Mental Disorders section to the Neurological section in the ICD.
Treatment for circadian rhythm sleep disorders
Possible treatments for circadian rhythm sleep disorders include:- Behavior therapy where the patient is told to avoid naps, caffeine, and other stimulants. They are also told to not be in bed for anything besides sleep and sex.
- Bright light therapyLight therapyLight therapy or phototherapy consists of exposure to daylight or to specific wavelengths of light using lasers, light-emitting diodes, fluorescent lamps, dichroic lamps or very bright, full-spectrum light, usually controlled with various devices...
is used to advance or delay sleep, depending on how the circadian rhythm is shifted. Patients are exposed to high-intensity light (up to 10,000 lux) for a duration of 30–60 minutes at a time, the time of day depending on whether an advance or a delay is required. - Medications such as melatoninMelatoninMelatonin , also known chemically as N-acetyl-5-methoxytryptamine, is a naturally occurring compound found in animals, plants, and microbes...
, a naturally occurring sleep aid, or other short term sleep aids or wake-promoting agents can be beneficial. TasimelteonTasimelteonTasimelteon is a drug which is under development for the treatment of insomnia and other sleep disorders. It is a selective agonist for the melatonin receptors MT1 and MT2 in the suprachiasmatic nucleus of the brain, similar to older drugs such as ramelteon...
has been proven effective in Phase III trials. - Sleep phase chronotherapy progressively advances or delays the sleep time by 1–2 hours per day.
See also
- ChronobiologyChronobiologyChronobiology is a field of biology that examines periodic phenomena in living organisms and their adaptation to solar- and lunar-related rhythms. These cycles are known as biological rhythms. Chronobiology comes from the ancient Greek χρόνος , and biology, which pertains to the study, or science,...
- ChronotypeChronotypeChronotype is an attribute of animals, including human beings, reflecting at what time of the day their physical functions are active, change or reach a certain level...
- Phase response curvePhase response curveA phase response curve illustrates the transient change in the cycle period of an oscillation induced by a perturbation as a function of the phase at which it is received...
- Sleep diarySleep diaryA sleep diary is a record of an individual's sleeping and waking times with related information, usually over a period of several weeks. It is self-reported or can be recorded by a care-giver....
- Sleep medicineSleep medicineSleep medicine is a medical specialty or subspecialty devoted to the diagnosis and therapy of sleep disturbances and disorders. From the middle of the 20th century, research has provided increasing knowledge and answered many questions about sleep-wake functioning. The rapidly evolving field has...
External links
- Circadian Rhythm Sleep Disorder on Psychnet-UK
- An American Academy of Sleep Medicine Review: Circadian Rhythm Sleep Disorders: Part I, Basic Principles, Shift Work and Jet Lag Disorders. PDF, 24 pages. November 2007.
- An American Academy of Sleep Medicine Review: Circadian Rhythm Sleep Disorders: Part II, Advanced Sleep Phase Disorder, Delayed Sleep Phase Disorder, Free-Running Disorder, and Irregular Sleep-Wake Rhythm. PDF, 18 pages. November 2007.
- An American Academy of Sleep Medicine Report: Practice Parameters for the Clinical Evaluation and Treatment of Circadian Rhythm Sleep Disorders, November 1, 2007
- NASA Sleep-Wake Actigraphy and Light Exposure During Spaceflight-Long Experiment
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