Non-24-hour sleep–wake disorder
| Non-24-hour sleep–wake disorder | |
|---|---|
| Other names | Hypernychthemeral syndrome, free-running disorder |
| Actogram of a sleep–wake pattern in non-24-hour sleep–wake disorder | |
| Specialty | Neurology |
| Symptoms | Progressively shifting nighttime |
| Complications | None if sleeping according to biological clock, sleep deprivation otherwise |
| Duration | Lifetime |
| Causes | Blindness for the blind, unknown cause for the sighted |
| Diagnostic method | Sleep diary, actigraphy |
| Treatment | Medication |
| Medication | Tasimelteon, melatonin |
| Frequency | 50–70% of totally (without light perception) blind people, less prevalent in sighted |
Non-24-hour sleep–wake disorder (non-24,[1] N24SWD,[2] or N24) is one of several chronic circadian rhythm sleep disorders (CRSDs). It is defined as a "chronic steady pattern comprising [...] daily delays in sleep onset and wake times in an individual living in a society".[3] Symptoms result when the non-entrained (free-running) endogenous circadian rhythm drifts out of alignment with the light–dark cycle in nature. Although this sleep disorder is more common in blind people, affecting up to 70% of the totally blind,[4] it can also affect sighted people. Non-24 may also be comorbid with bipolar disorder, depression, and traumatic brain injury.[2] The American Academy of Sleep Medicine (AASM) has provided CRSD guidelines since 2007 with the latest update released in 2015.[2][5]
People with non-24 experience daily shifts in the circadian rhythm such as peak time of alertness, body temperature minimum, metabolism and hormone secretion. These shifts do not align with the natural light–dark cycle. Non-24-hour sleep–wake disorder causes a person's sleep–wake cycle to move around the clock every day, to a degree dependent on the length of the cycle. This is known as free-running sleep.
People with the disorder may have an especially hard time adjusting to changes in "regular" sleep–wake cycles, such as vacations, stress, evening activities, time changes like daylight saving time, travel to different time zones, illness, medications (especially stimulants or sedatives), changes in daylight hours in different seasons, and growth spurts, which are typically known to cause fatigue. They also show lower sleep propensity after total sleep deprivation than do normal sleepers.[6]
Non-24 can begin at any age, not uncommonly in childhood. It is sometimes preceded by delayed sleep phase disorder.[7]
Most people with this disorder find that it severely impairs their ability to function in school, in employment, and in their social lives. Typically, they are "partially or totally unable to function in scheduled activities on a daily basis, and most cannot work at conventional jobs".[3] Attempts to keep conventional hours by people with the disorder generally result in insomnia (which is not a normal feature of the disorder itself) and excessive sleepiness,[3] to the point of falling into microsleeps, as well as myriad effects associated with acute and chronic sleep deprivation. People with non-24 who force themselves to live to a normal workday "are not often successful and may develop physical and psychological complaints during waking hours, i.e. sleepiness, fatigue, headache, decreased appetite, or depressed mood. Patients often have difficulty maintaining ordinary social lives, and some of them lose their jobs or fail to attend school."[6]
- ^ Fadden JS (May 12, 2015). "What You Need to Know About Non-24". Sleep Review. Retrieved June 26, 2019.
- ^ a b c Auger RR, Burgess HJ, Emens JS, Deriy LV, Thomas SM, Sharkey KM (October 15, 2015). "Clinical Practice Guideline for the Treatment of Intrinsic Circadian Rhythm Sleep–Wake Disorders: Advanced Sleep–Wake Phase Disorder (ASWPD), Delayed Sleep–Wake Phase Disorder (DSWPD), Non-24-Hour Sleep–Wake Rhythm Disorder (N24SWD), and Irregular Sleep–Wake Rhythm Disorder (ISWRD). An Update for 2015: An American Academy of Sleep Medicine Clinical Practice Guideline". Journal of Clinical Sleep Medicine. 11 (10): 1199–236. doi:10.5664/jcsm.5100. PMC 4582061. PMID 26414986.
- ^ a b c American Academy of Sleep Medicine (2001). The International Classification of Sleep Disorders, Revised (ICSD-R) (PDF). American Sleep Disorders Association. ISBN 978-0-9657220-1-8. Archived from the original (PDF) on July 26, 2011. Retrieved April 30, 2016.
- ^ "Non-24-Hour Sleep-Wake Disorder". NORD (National Organization for Rare Disorders). Retrieved December 14, 2020.
- ^ Morgenthaler TI, Lee-Chiong T, Alessi C, Friedman L, Aurora RN, Boehlecke B, Brown T, Chesson AL J, Kapur V, Maganti R, Owens J, Pancer J, Swick TJ, Zak R, Standards of Practice Committee of the American Academy of Sleep M (November 2007). "Practice parameters for the clinical evaluation and treatment of circadian rhythm sleep disorders. An American Academy of Sleep Medicine report". Sleep. 30 (11): 1445–59. doi:10.1093/sleep/30.11.1445. PMC 2082098. PMID 18041479.
- ^ a b Okawa M, Uchiyama M (December 2007). "Circadian rhythm sleep disorders: characteristics and entrainment pathology in delayed sleep phase and non-24-h sleep–wake syndrome" (PDF). Sleep Med Rev. 11 (6): 485–96. doi:10.1016/j.smrv.2007.08.001. PMID 17964201. Archived from the original (PDF) on December 17, 2008.
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