Non-24-hour sleep–wake disorder
Non-24-Hour Sleep-Wake Disorder in Blind Individuals: – Estimated occurrence in over half of totally blind individuals – Can develop at any age, especially after eye […]
Non-24-Hour Sleep-Wake Disorder in Blind Individuals:
– Estimated occurrence in over half of totally blind individuals
– Can develop at any age, especially after eye loss
– Suprachiasmatic nucleus (SCN) not synchronized without light input
– Rare in visually impaired with some light perception
– Minimal light exposure can impact body clock
– Up to 70% of totally blind individuals may have non-24
– Approximately 65,000 to 95,000 Americans with no light perception may have non-24
– Melatonin administration has shown improvement in sleep patterns for totally blind individuals
Symptoms, Causes, and Impact of Non-24-Hour Sleep-Wake Disorder:
– Difficulty following regular clock schedule
– Shifted biological clock causing daytime sleepiness and nighttime insomnia
– Cyclical nature with alternating symptomatic and asymptomatic periods
– Weight gain and hallucinations reported
– Extrinsic factors: isolation from natural light cycles
– Intrinsic factors: blindness or light response malfunction affecting melatonin release
– Neurological involvement, potentially linked to the suprachiasmatic nucleus (SCN)
– Impairs daily functioning in school, work, and social life
– Difficulty adjusting to changes in sleep-wake cycles
– Insomnia and excessive sleepiness common
– Physical and psychological complaints due to chronic sleep deprivation
– Difficulty maintaining social lives and employment, leading to job loss or school absenteeism
Non-24-Hour Sleep-Wake Disorder in Sighted Individuals:
– Etiology less understood compared to blind individuals
– Cases linked to head injury or pituitary adenoma
– Involves abnormal functioning of the suprachiasmatic nucleus (SCN)
– Failure of entrainment and abnormal reaction to light observed
– Longer sleep-wake cycle duration and core body temperature changes noted
Mechanisms, Diagnosis, and Medical Classification of Non-24-Hour Sleep-Wake Disorder:
– Human circadian rhythm averages 24 hours and 20 minutes
– Exposure to environmental time cues synchronizes the circadian clock
– Diagnosis based on a history of delayed sleep onset following a non-24-hour pattern
– International Classification of Sleep Disorders (ICSD) recognizes non-24 as a disorder
– Codes for non-24 include ICSD-3, ICD-9-CM, and ICD-10-CM
– The American Psychiatric Association acknowledges non-24 in the DSM-5
Treatment Options and Research on Non-24-Hour Sleep-Wake Disorder:
– Tasimelteon is an FDA-approved melatonin agonist for non-24 in blind individuals
– Melatonin supplementation has shown positive results in treating non-24
– Melatonin administration before bedtime treats inability to sleep but may not improve daytime sleepiness
– Light therapy involves exposure to bright white or blue light to counteract circadian rhythm delays
– Ongoing research is focused on developing new treatments for circadian rhythm sleep disorders
– Studies explore the pathology of circadian rhythm sleep disorders
– Melatonin plays a crucial role in regulating sleep-wake cycles
This article possibly contains original research. (November 2018) |
Non-24-hour sleep–wake disorder (non-24 or N24SWD) 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". 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, it can also affect sighted people. Non-24 may also be comorbid with bipolar disorder, depression, and traumatic brain injury. The American Academy of Sleep Medicine (AASM) has provided CRSD guidelines since 2007 with the latest update released in 2015.
| Non-24-hour sleep–wake disorder | |
|---|---|
| Other names | Hypernychthemeral syndrome, free-running 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 |
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.[citation needed]
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.
Non-24 can begin at any age, not uncommonly in childhood. It is sometimes preceded by delayed sleep phase disorder.
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". 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, 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."