{{short description|Family of sleep disorders that affect the timing of sleep}} {{redirect|CRSD|the Oracle Cluster Ready Services daemon (CRSd)|Oracle Clusterware|the school district in Alaska|Copper River School District|the school district in Delaware|Caesar Rodney School District}} thumb|Types of Circadian rhythm sleep disorder {{use dmy dates|date=June 2023}} {{cs1 config|name-list-style=vanc|display-authors=6}} {{Infobox medical condition (new) | name = Circadian rhythm sleep disorder | synonyms = Circadian rhythm sleep–wake disorders | field = Sleep medicine, psychiatry, neurology, chronobiology | symptoms = | complications = | onset = | duration = | types = | causes = | risks = | diagnosis = | differential = | prevention = | treatment = | medication = | prognosis = | frequency = | deaths = | image = | alt = | caption = }} '''Circadian rhythm sleep disorders''' ('''CRSD'''), also known as '''circadian rhythm sleep–wake disorders''' ('''CRSWD'''), are a family of sleep disorders that affect the timing of sleep. CRSDs cause a persistent pattern of sleep/wake disturbances that arise either by dysfunction in one's biological clock system, or by misalignment between one's endogenous oscillator and externally imposed cues. As a result of this misalignment, those affected by circadian rhythm sleep disorders can fall asleep at unconventional time points in the day, or experience excessive daytime sleepiness if they resist. These occurrences often lead to recurring instances of disrupted rest and wakefulness, where individuals affected by the disorder are unable to go to sleep and awaken at "normal" times for work, school, and other social obligations. Delayed sleep phase disorder, advanced sleep phase disorder, non-24-hour sleep–wake disorder and irregular sleep–wake rhythm disorder represent the four main types of CRSD.<ref>{{cite journal | vauthors = Dagan Y | title = Circadian Rhythm Sleep Disorders (CRSD) in psychiatry--a review | journal = The Israel Journal of Psychiatry and Related Sciences | volume = 39 | issue = 1 | pages = 19–27 | date = 2002 | pmid = 12013706 }}</ref>
== Overview == Humans, like most living organisms, have various biological rhythms. These biological clocks control processes that fluctuate daily (e.g., body temperature, alertness, hormone secretion), generating circadian rhythms. Among these physiological characteristics, the sleep–wake propensity can also be considered one of the daily rhythms regulated by the biological clock system. Humans' sleeping cycles are tightly regulated by a series of circadian processes working in tandem, allowing for the experience of moments of consolidated sleep during the night and a long wakeful moment during the day. ipRGCs (intrinsically photosensitive retinal ganglion cells), for example, are involved in modulating the circadian rhythm because of the expression of melanopsin, which absorbs light in the blue part (around 480 nm).<ref>{{cite journal | vauthors = Menéndez-Velázquez A, Morales D, García-Delgado AB | title = Light Pollution and Circadian Misalignment: A Healthy, Blue-Free, White Light-Emitting Diode to Avoid Chronodisruption | journal = International Journal of Environmental Research and Public Health | volume = 19 | issue = 3 | page = 1849 | date = February 2022 | pmid = 35162871 | pmc = 8835293 | doi = 10.3390/ijerph19031849 | doi-access = free }}</ref> Conversely, disruptions to these processes and the communication pathways between them can lead to problems in sleeping patterns,<ref name="Silvani-2022">{{cite journal | vauthors = Silvani MI, Werder R, Perret C | title = The influence of blue light on sleep, performance and wellbeing in young adults: A systematic review | journal = Frontiers in Physiology | volume = 13 | article-number = 943108 | date = August 16, 2022 | pmid = 36051910 | pmc = 9424753 | doi = 10.3389/fphys.2022.943108 | doi-access = free }}</ref> which are collectively referred to as circadian rhythm sleep disorders.
== Normal rhythm == A circadian rhythm is an entrainable, endogenous, biological activity that has a period of roughly twenty-four hours. This internal time-keeping mechanism is centralized in the suprachiasmatic nucleus (SCN) of humans, and allows for the internal physiological mechanisms underlying sleep and alertness to become synchronized to external environmental cues, like the light-dark cycle.<ref>{{cite journal | vauthors = Toh KL | title = Basic science review on circadian rhythm biology and circadian sleep disorders | journal = Annals of the Academy of Medicine, Singapore | volume = 37 | issue = 8 | pages = 662–8 | date = August 2008 | doi = 10.47102/annals-acadmedsg.V37N8p662 | pmid = 18797559 | s2cid = 11071556 | doi-access = free }}</ref> The SCN also sends signals to peripheral clocks in other organs, like the liver, to control processes such as glucose metabolism.<ref>{{cite journal | vauthors = Dibner C, Schibler U, Albrecht U | title = The mammalian circadian timing system: organization and coordination of central and peripheral clocks | journal = Annual Review of Physiology | volume = 72 | issue = 1 | pages = 517–49 | date = 2010-03-17 | pmid = 20148687 | doi = 10.1146/annurev-physiol-021909-135821 | url = http://doc.rero.ch/record/17505/files/alb_mct.pdf }}</ref> Although these rhythms will persist in constant light or dark conditions, different zeitgebers (time givers such as the light-dark cycle) give context to the clock and allow it to entrain and regulate expression of physiological processes to adjust to the changing environment. Genes that help control light-induced entrainment include positive regulators BMAL1 and CLOCK and negative regulators PER1 and CRY.<ref>{{cite journal | vauthors = Dunlap JC | title = Molecular bases for circadian clocks | journal = Cell | volume = 96 | issue = 2 | pages = 271–90 | date = January 1999 | pmid = 9988221 | doi=10.1016/s0092-8674(00)80566-8| s2cid = 14991100 | doi-access = free }}</ref> A full circadian cycle can be described as a twenty-four hour circadian day, where circadian time zero (CT 0) marks the beginning of a subjective day for an organism and CT 12 marks the start of subjective night.<ref>{{cite journal | vauthors = Vitaterna MH, Takahashi JS, Turek FW | title = Overview of circadian rhythms | journal = Alcohol Research & Health | volume = 25 | issue = 2 | pages = 85–93 | date = December 2001 | pmid = 11584554 | pmc = 6707128 }}</ref>
Humans with regular circadian function have been shown to maintain regular sleep schedules, regulate daily rhythms in hormone secretion, and sustain oscillations in core body temperature.<ref>{{cite journal | vauthors = Farhud D, Aryan Z | title = Circadian Rhythm, Lifestyle and Health: A Narrative Review | journal = Iranian Journal of Public Health | volume = 47 | issue = 8 | pages = 1068–1076 | date = August 2018 | pmid = 30186777 | pmc = 6123576 }}</ref> Even in the absence of zeitgebers, humans will continue to maintain a roughly 24-hour rhythm in these biological activities. Regarding sleep, normal circadian function allows people to maintain balance rest and wakefulness that allows people to work and maintain alertness during the day's activities, and rest at night.<ref>{{cite web|url=https://www.sleepfoundation.org/articles/sleep-drive-and-your-body-clock|title=Body Clock & Sleep - National Sleep Foundation|website=www.sleepfoundation.org|access-date=2019-04-10}}</ref>
Some misconceptions regarding circadian rhythms and sleep commonly mislabel irregular sleep as a CRSD. In order to be diagnosed with CRSD, there must be either a misalignment between the timing of the circadian oscillator and the surrounding environment, or failure in the clock entrainment pathway.<ref name="Dodson_2010">{{cite journal | vauthors = Dodson ER, Zee PC | title = Therapeutics for Circadian Rhythm Sleep Disorders | journal = Sleep Medicine Clinics | volume = 5 | issue = 4 | pages = 701–715 | date = December 2010 | pmid = 21243069 | pmc = 3020104 | doi = 10.1016/j.jsmc.2010.08.001 }}</ref> Among people with typical circadian clock function, there is variation in chronotypes, or preferred wake and sleep times, of individuals. Although chronotype varies from individual to individual, as determined by rhythmic expression of clock genes, people with typical circadian clock function will be able to entrain to environmental cues. For example, if a person wishes to shift the onset of a biological activity, like waking time, light exposure during the late subjective night or early subjective morning can help advance one's circadian cycle earlier in the day, leading to an earlier wake time.<ref name="Zhu_2012">{{cite journal | vauthors = Zhu L, Zee PC | title = Circadian rhythm sleep disorders | journal = Neurologic Clinics | volume = 30 | issue = 4 | pages = 1167–91 | date = November 2012 | pmid = 23099133 | pmc = 3523094 | doi = 10.1016/j.ncl.2012.08.011 }}</ref>
== Diagnosis == The International Classification of Sleep Disorders classifies CRSD as a type of sleep dyssomnia.<ref name="Kim_2013" /> Although studies suggest that 3% of the adult population has a CRSD, many people are often misdiagnosed with insomnia instead of a CRSD. Of adults diagnosed with sleep disorders, an estimated 10% have a CRSD and of adolescents with sleep disorders, an estimated 16% may have a CRSD.<ref name="Kim_2013" /> Patients diagnosed with circadian rhythm sleep disorders typically express a pattern of disturbed sleep, whether that be excessive sleep that intrudes on working schedules and daily functions, or insomnia at desired times of sleep. Note that having a preference for extreme early or late wake times is not related to a circadian rhythm sleep disorder diagnosis. There must be distinct impairment of biological rhythms that affects the person's desired work and daily behavior. For a CRSD diagnosis, a sleep specialist gathers the history of a patient's sleep and wake habits, body temperature patterns, and dim-light melatonin onset (DLMO).<ref name="Kim_2013">{{cite journal | vauthors = Kim MJ, Lee JH, Duffy JF | title = Circadian Rhythm Sleep Disorders | journal = Journal of Clinical Outcomes Management | volume = 20 | issue = 11 | pages = 513–528 | date = November 2013 | pmid = 25368503 | pmc = 4212693 }}</ref> Gathering this data gives insight into the patient's current schedule, as well as the physiological phase markers of the patient's biological clock.<ref name="Behavioral and psychiatric conseque">{{cite journal | vauthors = Dagan Y, Borodkin K | title = Behavioral and psychiatric consequences of sleep-wake schedule disorders | journal = Dialogues in Clinical Neuroscience | volume = 7 | issue = 4 | pages = 357–365 | date = December 2005 | pmid = 16416711 | pmc = 3181741 | doi = 10.31887/DCNS.2005.7.4/ydagan }}</ref>
The start of the CRSD diagnostic process is a thorough sleep history assessment. A standard questionnaire is used to record the sleep habits of the patient, including typical bedtime, sleep duration, sleep latency, and instances of waking up. The professional will further inquire about other external factors that may impact sleep. Prescription drugs that treat mood disorders like tricyclic antidepressants, selective serotonin reuptake inhibitors and other antidepressants are associated with abnormal sleep behaviors. Other daily habits like work schedule and timing of exercise are also recorded—because they may impact an individual's sleep and wake patterns. To measure sleep variables candidly, patients wear actigraphy watches that record sleep onset, wake time, and many other physiological variables. Patients are similarly asked to self-report their sleep habits with a week-long sleep diary to document when they go to bed, when they wake up, etc. to supplement the actigraphy data. Collecting this data allows sleep professionals to carefully document and measure patient's sleep habits and confirm patterns described in their sleep history.<ref name="Kim_2013" />
Other additional ways to classify the nature of a patient's sleep and biological clock are the morningness-eveningness questionnaire (MEQ) and the Munich ChronoType Questionnaire, both of which have fairly strong correlations with accurately reporting phase advanced or delayed sleep.<ref name="Zhu_2012" /> Questionnaires like the Pittsburgh Sleep Quality Index (PSQI) and the Insomnia Severity Index (ISI) help gauge the severity of sleep disruption. Specifically, these questionnaires can help the professional assess the patient's problems with sleep latency, undesired early-morning wakefulness, and problems with falling or staying asleep.<ref name="Kim_2013" /> Tayside children's sleep questionnaire is a ten-item questionnaire for sleep disorders in children aged between one and five years old.<ref>{{cite journal | vauthors = McGreavey JA, Donnan PT, Pagliari HC, Sullivan FM | title = The Tayside children's sleep questionnaire: a simple tool to evaluate sleep problems in young children | journal = Child | volume = 31 | issue = 5 | pages = 539–544 | date = September 2005 | pmid = 16101649 | doi = 10.1111/j.1365-2214.2005.00548.x }}</ref><ref>{{Cite web|title=Tayside Children's Sleep Questionnaire (TCSQ)|url=https://www.thoracic.org/members/assemblies/assemblies/srn/questionaires/tcsq.php|access-date=2021-07-21|website=www.thoracic.org|archive-date=10 July 2023|archive-url=https://web.archive.org/web/20230710213140/https://www.thoracic.org/members/assemblies/assemblies/srn/questionaires/tcsq.php}}</ref><ref>{{cite journal | vauthors = Rajaee Rizi F, Asgarian FS | title = Reliability, validity, and psychometric properties of the Persian version of the Tayside children's sleep questionnaire | journal = Sleep and Biological Rhythms | volume = 21 | issue = 1 | pages = 97–103 | date = January 2023 | pmid = 38468908 | pmc = 10899986 | doi = 10.1007/s41105-022-00420-6 | s2cid = 245863909 }}</ref>
A sleep study may be employed.
== Types == thumb|Categories and types of Circadian rhythm sleep disorder Currently, the International Classification of Sleep Disorders (ICSD-3) lists 6 disorders under the category of circadian rhythm sleep disorders.<ref name="Sateia_2014">{{cite journal | vauthors = Sateia MJ | title = International classification of sleep disorders-third edition: highlights and modifications | journal = Chest | volume = 146 | issue = 5 | pages = 1387–1394 | date = November 2014 | pmid = 25367475 | doi = 10.1378/chest.14-0970 }}</ref>
CRSDs can be categorized into two groups based on their underlying mechanisms: The first category is composed of disorders where the endogenous oscillator has been altered, known as intrinsic type disorders. The second category consists of disorders in which the external environment and the endogenous circadian clock are misaligned, called extrinsic type CRSDs.<ref>{{cite journal | vauthors = Zhu L, Zee PC | title = Circadian rhythm sleep disorders | journal = Neurologic Clinics | volume = 30 | issue = 4 | pages = 1167–1191 | date = November 2012 | pmid = 23099133 | pmc = 3523094 | doi = 10.1016/j.ncl.2012.08.011 }}</ref>
=== Intrinsic === * Delayed sleep phase disorder (DSPD): Individuals who have been diagnosed with delayed sleep phase disorder have sleep–wake times that are delayed when compared to normal functioning individuals. People with DSPD typically have very long periods of sleep latency when they attempt to go to sleep during conventional sleeping times. Similarly, they also have trouble waking up at conventional times.<ref>{{cite web |url= https://www.lecturio.com/concepts/circadian-rhythm-sleep-wake-disorder/ |title= Circadian Rhythm Sleep–Wake Disorder |website= The Lecturio Medical Concept Library |access-date=2021-06-24}}</ref> * Advanced sleep phase disorder (ASPD): People with advanced sleep phase disorder exhibit characteristics opposite to those with delayed sleep phase disorder. These individuals have advanced sleep–wake times, so they tend to go to bed and wake up much earlier as compared to normal individuals. ASPD is less common than DSPD, and is most prevalent within older populations.<ref name="Behavioral and psychiatric conseque"/> ** Familial advanced sleep phase syndrome (FASPS) is linked to an autosomal dominant mode of inheritance. It is associated with a missense mutation in human PER2 that replaces serine for glycine at position 662 (S662G).<ref>{{cite journal | vauthors = Jones CR, Huang AL, Ptáček LJ, Fu YH | title = Genetic basis of human circadian rhythm disorders | journal = Experimental Neurology | volume = 243 | pages = 28–33 | date = May 2013 | pmid = 22849821 | pmc = 3514403 | doi = 10.1016/j.expneurol.2012.07.012 }}</ref> * Irregular sleep–wake rhythm disorder (ISWRD) is characterized by a normal 24 hour sleeping period. However, individuals with this disorder experience fragmented and highly disorganized sleep that can manifest in the form of waking frequently during the night and taking naps during the day, yet still maintaining sufficient total time asleep. People with ISWRD often experience a range of symptoms from insomnia to excessive daytime sleepiness.<ref name="Behavioral and psychiatric conseque"/> * Non-24-hour sleep–wake disorder (N24SWD): Most common in individuals that are blind and unable to detect light, is characterized by chronic patterns of sleep/wake cycles that are not entrained to the 24 hour light–dark environmental cycle. As a result of this, individuals with this disorder will usually experience a gradual yet predictable delay of sleep onset and waking times. Patients with DSPD may develop this disorder if their condition is untreated.<ref name="Behavioral and psychiatric conseque"/>
=== Extrinsic === * Shift work sleep disorder (SWSD): Approximately 9% of Americans who work night or irregular work shifts are believed to experience shift work sleep disorder.<ref>{{cite journal | vauthors = Di Milia L, Waage S, Pallesen S, Bjorvatn B | title = Shift work disorder in a random population sample--prevalence and comorbidities | journal = PLOS ONE | volume = 8 | issue = 1 | article-number = e55306 | date = 2013-01-25 | pmid = 23372847 | pmc = 3555931 | doi = 10.1371/journal.pone.0055306 | veditors = Gamble KL | bibcode = 2013PLoSO...855306D | doi-access = free }}</ref> Night shift work directly opposes the environmental cues that entrain our biological clock, so this disorder arises when an individual's clock is unable to adjust to the socially imposed work schedule. Shift work sleep disorder can lead to severe cases of insomnia as well as excessive daytime sleepiness.<ref>{{cite web |url= https://www.lecturio.com/concepts/circadian-rhythm-sleep-wake-disorder/ |title= Circadian Rhythm Sleep–Wake Disorder |website= The Lecturio Medical Concept Library |access-date=2021-06-24}}</ref> * Jet lag: Jet lag is best characterized by difficulty falling asleep or staying asleep as a result of misalignment between one's internal circadian system and external, or environmental cues. It is typically associated with rapid travel across multiple time zones.<ref name="Sateia_2014" />
== Alzheimer's disease == CRSD has been frequently associated with excessive daytime sleepiness and nighttime insomnia in patients diagnosed with Alzheimer's disease (AD), representing a common characteristic among AD patients as well as a risk factor of progressive functional impairments.<ref name="Malkani_2015">{{cite journal | vauthors = Malkani R, Attarian H | title = Sleep in neurodegenerative disorders. | journal = Current Sleep Medicine Reports | date = June 2015 | volume = 1 | issue = 2 | pages = 81–90 | doi = 10.1007/s40675-015-0016-x }}</ref><ref name="Dick-Muehlke_2015">{{cite book | vauthors = Dick-Muehlke C, Li R, Orleans M |title=Psychosocial studies of the individual's changing perspectives in Alzheimer's disease |date=2015 |publisher=Medical Information Science Reference |location=Hershey, PA |isbn=978-1-4666-8479-9}}</ref><ref name="Zhong_2011" /> On one hand, it has been stated that people with AD have melatonin alteration and high irregularity in their circadian rhythm that lead to a disrupted sleep–wake cycle, probably due to damage on hypothalamic SCN regions typically observed in AD.<ref name="Dick-Muehlke_2015" /><ref name="Zhong_2011" /> On the other hand, disturbed sleep and wakefulness states have been related to worsening of an AD patient's cognitive abilities, emotional state and quality of life.<ref name="Malkani_2015" /><ref name="Dick-Muehlke_2015" /><ref name="Zhong_2011">{{cite journal | vauthors = Zhong G, Naismith SL, Rogers NL, Lewis SJ | year = 2011 | title = Sleep–wake disturbances in common neurodegenerative diseases: A closer look at selected aspects of the neural circuitry | doi = 10.1016/j.jns.2011.04.020 | journal = Journal of the Neurological Sciences | volume = 307 | issue = 1–2| pages = 9–14 | pmid = 21570695 | s2cid = 44744844 }}</ref> Moreover, the abnormal behavioural symptoms of the disease negatively contribute to overwhelming patients' relatives and caregivers as well.<ref name="Malkani_2015" /><ref name="Dick-Muehlke_2015" />
However, the impact of sleep–wake disturbances on the subjective experience of a person with AD is not yet fully understood.<ref name="Dick-Muehlke_2015" /> Therefore, further studies exploring this field have been highly recommended, mainly considering the increasing life expectancy and significance of neurodegenerative diseases in clinical practices.<ref name="Zhong_2011" />
== Treatment == {{See also|List of investigational chronobiotics}}
Possible treatments for circadian rhythm sleep disorders include:
* Chronotherapy has been shown to effectively treat delayed sleep phase disorder; it acts by systematically delaying an individual's bedtime until their sleep–wake times coincide with the conventional 24 h day.<ref>{{Cite web|url=https://www.webmd.com/sleep-disorders/behavioral-treatment-circadian-rhythm-disorders|title=Behavioral Treatment of Circadian Rhythm Disorder|website=WebMD|language=en|access-date=2021-06-24}}</ref> * Light therapy utilizes bright light exposure to induce phase advances and delays in sleep and wake times. This therapy requires 30–60 minutes of exposure to a bright ({{val|5,000|–|10,000|u=lux}}) white, blue, or natural light at a set time until the circadian clock is aligned with the desired schedule.<ref name="Dodson_2010" /><ref name="Dagan_2002">{{cite journal | vauthors = Dagan Y | s2cid = 45059503 | title = Circadian rhythm sleep disorders (CRSD) | journal = Sleep Medicine Reviews | volume = 6 | issue = 1 | pages = 45–54 | date = February 2002 | pmid = 12531141 | doi = 10.1053/smrv.2001.0190 }}</ref> Treatment is initially administered either upon awakening or before sleeping, and if successful may be continued indefinitely or performed less frequently.<ref>{{cite journal | vauthors = Dijk DJ, Boulos Z, Eastman CI, Lewy AJ, Campbell SS, Terman M | s2cid = 9788704 | title = Light treatment for sleep disorders: consensus report. II. Basic properties of circadian physiology and sleep regulation | journal = Journal of Biological Rhythms | volume = 10 | issue = 2 | pages = 113–25 | date = June 1995 | pmid = 7632985 | doi = 10.1177/074873049501000204 }}</ref> Though proven very effective in the treatment of individuals with DSPD and ASPD, the benefits of light therapy on N24SWD, shift work disorder, and jet lag have not been studied as extensively. * Hypnotics have also been used clinically alongside bright light exposure therapy and pharmacotherapy for the treatment of CRSDs such as Advanced Sleep Phase Disorder.<ref>{{cite journal | vauthors = Barion A, Zee PC | title = A clinical approach to circadian rhythm sleep disorders | journal = Sleep Medicine | volume = 8 | issue = 6 | pages = 566–77 | date = September 2007 | pmid = 17395535 | pmc = 2679862 | doi = 10.1016/j.sleep.2006.11.017 }}</ref> Additionally, in conjunction with cognitive behavioral therapy, short-acting hypnotics also present an avenue for treating co-morbid insomnia in patients with circadian sleep disorders.<ref name="urlDorlands Medical Dictionary:hypnotic">{{cite web|url=http://www.mercksource.com/pp/us/cns/cns_hl_dorlands_split.jsp?pg=/ppdocs/us/common/dorlands/dorland/four/000051451.htm |title=Dorlands Medical Dictionary:hypnotic |website=Mercksource.com |archive-url=https://web.archive.org/web/20081211091401/http://www.mercksource.com/pp/us/cns/cns_hl_dorlands_split.jsp?pg=%2Fppdocs%2Fus%2Fcommon%2Fdorlands%2Fdorland%2Ffour%2F000051451.htm |archive-date=2008-12-11 }}</ref> * Melatonin, a naturally occurring biological hormone with circadian rhythmicity, has been shown to promote sleep and entrainment to external cues when administered in drug form (0.5–5.0 mg). Melatonin administered in the evening causes phase advances in sleep–wake times while maintaining duration and quality of sleep. Similarly, when administered in the early morning, melatonin can cause phase delays. It has been shown most effective in cases of shift work sleep disorder and delayed phase sleep disorder, but has not been proven particularly useful in cases of jet lag.<ref name="Dagan_2002" /> * Dark therapy, for example, the use of blue-blocking goggles, is used to block blue and blue-green wavelength light from reaching the eye during evening hours so as not to hinder melatonin production.<ref>{{cite web | title = Blue light has a dark side | url = http://www.health.harvard.edu/newsletters/Harvard_Health_Letter/2012/May/blue-light-has-a-dark-side/ | date = May 2012 | work = Harvard Health Letter }}</ref>
== See also == {{col div|colwidth=30em}} * Chronobiology * Familial sleep traits * Light effects on circadian rhythm * Phase response curve * Sleep diary * Sleep medicine {{colend}}
== References == {{reflist}}
== External links == {{Medical resources | ICD10 = {{ICD10|F|51|2|f|50}}, {{ICD10|G|47|2|g|40}} | ICD9 = {{ICD9|327.3}}, {{ICD9|780.55}} | MeshID = D021081 }} * [http://www.circadiansleepdisorders.org Circadian Sleep Disorders Network] * [http://www.journalsleep.org/Articles/301107.pdf 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.] {{Webarchive|url=https://web.archive.org/web/20170808212941/http://www.journalsleep.org/Articles/301107.pdf |date=8 August 2017 }} * [http://www.journalsleep.org/Articles/301108.pdf 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.] * [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2082098/ An American Academy of Sleep Medicine Report: ''Practice Parameters for the Clinical Evaluation and Treatment of Circadian Rhythm Sleep Disorders'', November 1, 2007] * [https://web.archive.org/web/20080916102107/http://www.nasa.gov/mission_pages/station/science/experiments/Sleep-Long.html NASA Sleep–Wake Actigraphy and Light Exposure During Spaceflight-Long Experiment]
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{{DEFAULTSORT:Circadian Rhythm Sleep Disorder}} Category:Sleep disorders Category:Neurophysiology Category:Sleep physiology Category:Circadian rhythm sleep–wake disorders