Non-24-Hour Sleep-Wake Disorder
What is Non-24-Hour Sleep-Wake Disorder
Non-24-Hour Sleep-Wake Disorder, or Non-24, is a circadian rhythm disorder. Circadian rhythms are physical and behavioral changes that follow a daily sleep-wake cycle lasting approximately 24 hours. The sleep-wake cycle is an important feature of circadian rhythms.
Sleep-wake cycle that synchronizes with the environmental day-night cycle. In the absence of light and hormone regulation of sleep queues, natural sleep cycles may be longer or shorter than a true 24 hour period. Without the ability to perceive light, or in those having a disorder preventing the body from regulating sleep-wake cycles, a person’s sleep onset will shift later or earlier each day leading to periods of wakefulness at night and/or excessive sleepiness during the day. For example, if someone with Non-24 goes to sleep at 8 pm one night, they may not be able to fall asleep until 10 pm the next night. They will also need to sleep consistently later the next morning. This pattern continues delaying the sleep time each night to 12 am, then 2 am, then 4 am, and so on. People with Non-24 will experience periods of normal sleep as their sleep-wake cycle makes it around the clock and realigns with a regular day-night cycle. This may provide temporary relief, but symptoms will return as their sleep time moves out of sync again.
Non-24 is most common among non-sighted individuals who have no light perception, but can occur in sighted individuals.
How common is Non-24-Hour Sleep-Wake Disorder
Non-24 is a rare condition that occurs primarily non-sighted individuals who have no light perception It is estimated that Non-24 affects 50-70% of non-light perceiving blind individuals. Non-24 has also been reported in sighted people but the total number of people living with Non-24 is unknown.
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1. Fadden J, Sharkey K. "Non-24-Hour Sleep-Wake Disorder." NORD (National Organization for Rare Disorders). National Organization for Rare Disorders, 2017. Web. 6 Oct. 2017.
2. Uchiyama M, Lockley SW. Non-24-Hour Sleep-Wake Rhythm Disorder in Sighted and Blind Patients. Sleep Med Clin 2015; 10:495.
3. Auger RR, Burgess HJ, Emens JS, et al. 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. J Clin Sleep Med. 2015 Oct 15;11(10):1199-236.
4. Fadden, J. Can Chronotherapy Cause Non-24 (Q&A). Circadian Sleep Disorders Network. Last modified Aug 21, 2016.
5. Emens JS, Eastman CI. Diagnosis and Treatment of Non-24-h Sleep-Wake Disorder in the Blind. Drugs. 2017 Apr;77(6):637-650.
6. Auger RR, Burgess HJ, Emens JS, et al. 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. J Clin Sleep Med. 2015 Oct 15;11(10):1199-236.
What are the symptoms of Non-24-Hour Sleep-Wake Disorder
Symptoms of Non-24 are characterized by cyclic episodes of wakefulness at night and/or excessive daytime sleepiness followed by episodes of normal sleep.
Chronic sleep loss has been associated with the development of other conditions such as cardiovascular disease, obesity, diabetes, and depression.
How is it diagnosed
Initial diagnosis of Non-24 is based on sleep logs kept by the patient. A doctor will have a patient document sleep times and wake times in a sleep log for at least 14 weeks. Actigraphy may be used to confirm diagnosis. Actigraphy is a continuous recording of movement with the use of a small device called an actigraph which is worn on the wrist. Sometimes polysomnography, an overnight sleep study, is used to rule out other related sleep disorders.
1. American Academy of Sleep Medicine. International Classification of Sleep Disorders, 3rd ed, American Academy of Sleep Medicine, Darien, IL 2014.
2. American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders. 5th ed. Arlington, VA: American Psychiatric Association; 2013
3. Colten HR, Altevogt BM, editors. Sleep Disorders and Sleep Deprivation: An Unmet Public Health Problem. Washington (DC): National Academies Press (US); 2006. 3, Extent and Health Consequences of Chronic Sleep Loss and Sleep Disorders.
4. American Academy of Sleep Medicine. International Classification of Sleep Disorders, 3rd ed, American Academy of Sleep Medicine, Darien, IL 2014.
5. American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders. 5th ed. Arlington, VA: American Psychiatric Association; 2013
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There are many organizations that support research and advocacy for Non-24-Hour Sleep-Wake Disorder. See below for a few of those organizations.
Non-24-Hour Sleep-Wake Disorder Organizations
- National Organization for Rare Disorders (NORD)
- Circadian Sleep Disorders Network
- American Sleep Association
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