Non-24-Hour Sleep-Wake Disorder
National Organization for Rare Disorders, Inc.
- free-running disorder
- circadian rhythm sleep disorder, free-running type
- hypernychthemeral syndrome
- non-24-hour disorder
- non-24-hour sleep-wake syndrome
- non-24-hour sleep-wake cycle disorder
Non-24-hour sleep-wake disorder (N24) is a circadian rhythm sleep disorder in which an individual's biological clock fails to synchronize to a 24-hour day. Instead of sleeping at roughly the same time every day, someone with N24 will typically find their sleep time gradually delaying by minutes to hours every day. They will sleep at later and later clock times until their sleep periods go all the way around the clock. (In extremely rare cases the sleep rhythm will gradually advance rather than delay.) Patients' cycles of body temperature and hormone rhythms also follow a non-24-hour rhythm. Attempts to fight against this internal rhythm and sleep on a normal schedule result in severe and cumulative sleep deprivation.
N24 occurs in roughly 50% of completely blind people but also occurs in an unknown number of sighted people.
Circadian Sleep Disorders Network
4619 Woodfield Rd.
Bethesda, MD 20814
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Last Updated: 3/26/2013
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