Non-24-Hour Sleep Wake Disorder

What Is Non-24-Hour Sleep-Wake Disorder?

Individuals with non-24-hour sleep-wake disorder Trusted Source Merck Manual First published in 1899 as a small reference book for physicians and pharmacists, the Manual grew in size and scope to become one of the most widely used comprehensive medical resources for professionals and consumers. View Source (N24SWD) have a circadian rhythm that is shorter or, more often, slightly longer than 24 hours. This causes sleep and wake times to get pushed progressively earlier or later, usually by one or two hours at a time. Over days or weeks, the circadian rhythm becomes desynchronized from regular daylight hours.

As a consequence of this ever-shifting rhythm, individuals with N24SWD experience inappropriate fluctuations in appetite, mood, and alertness. During periods when their body clock is heavily desynchronized, they show a natural preference for sleeping in the middle of the day and difficulty sleeping at night. Several weeks later, they may not show any symptoms at all as their internal clock catches up with daylight once more.

Attempts to maintain a regular sleep-wake cycle are unsuccessful Trusted Source National Library of Medicine, Biotech Information The National Center for Biotechnology Information advances science and health by providing access to biomedical and genomic information. View Source , even when supplemented by common solutions such as caffeine Trusted Source National Library of Medicine, Biotech Information The National Center for Biotechnology Information advances science and health by providing access to biomedical and genomic information. View Source . Over the long term, desynchronization from the innate circadian rhythm may have adverse health consequences Trusted Source National Library of Medicine, Biotech Information The National Center for Biotechnology Information advances science and health by providing access to biomedical and genomic information. View Source .

Individuals with non-24-hour sleep-wake disorder often have difficulty keeping work, school, or social commitments. They may develop depression Trusted Source National Library of Medicine, Biotech Information The National Center for Biotechnology Information advances science and health by providing access to biomedical and genomic information. View Source due to the stress of not being able to keep a normal schedule, or as a side effect of sleeping during the day and not getting enough sunlight.

Non-24-Hour Sleep-Wake Disorder vs. Other Circadian Disorders

Non-24-hour sleep-wake disorder is one of six circadian rhythm sleep disorders. It is considered an intrinsic sleep-wake disorder because the problem is mostly due to internal factors instead of external factors, such as jet lag or shift work.

Other intrinsic circadian rhythm disorders include advanced and delayed sleep-wake phase disorders, in which the sleep-wake cycle is pushed significantly forward or backward, and irregular sleep-wake rhythm disorder, in which individuals display a fragmented sleep-wake cycle with napping throughout the day and long periods awake at night.

What Causes Non-24-Hour Sleep-Wake Disorder?

Non-24-hour sleep-wake disorder is most common in people with total blindness Trusted Source National Library of Medicine, Biotech Information The National Center for Biotechnology Information advances science and health by providing access to biomedical and genomic information. View Source , due to the lack of light input reaching the internal clock. It’s estimated that approximately 50% of completely blind people have N24SWD. Not all blind people suffer from this disorder, because some retain the ability to perceive light Trusted Source National Library of Medicine, Biotech Information The National Center for Biotechnology Information advances science and health by providing access to biomedical and genomic information. View Source to a certain extent.

For many people with N24SWD, the circadian rhythm drifts faster when bedtime occurs during the day and slows down when bedtime coincides with night Trusted Source National Library of Medicine, Biotech Information The National Center for Biotechnology Information advances science and health by providing access to biomedical and genomic information. View Source . Researchers hypothesize that blind people may display a weak circadian response to factors such as sleep schedules, physical activity, and possibly even light, but not a strong enough response to establish a regular circadian rhythm.

Most people with N24SWD have between a 24 and a 25-hour sleep cycle. The further the cycle is from 24 hours, the faster disruptions to their sleep-wake schedule occur.

Can a Sighted Person Have Non-24-Hour Sleep-Wake Disorder?

Non-24-hour sleep-wake disorder can also happen in sighted people Trusted Source National Library of Medicine, Biotech Information The National Center for Biotechnology Information advances science and health by providing access to biomedical and genomic information. View Source . Symptoms manifest as generic daytime sleepiness and nighttime insomnia, so N24SWD is often misdiagnosed Trusted Source National Library of Medicine, Biotech Information The National Center for Biotechnology Information advances science and health by providing access to biomedical and genomic information. View Source as another sleep disorder in sighted people. As a result, many sighted people have the disorder for years before receiving a diagnosis.

It’s unclear what causes non-24-hour sleep-wake disorder in sighted people. The largest study ever done on sighted people with N24SWD found that the majority were male, with symptoms that started in the teens or twenties. Non-24-hour sleep-wake disorder may have a genetic component Trusted Source National Library of Medicine, Biotech Information The National Center for Biotechnology Information advances science and health by providing access to biomedical and genomic information. View Source , though it rarely runs in families and may not develop unless a person has more than one risk factor Trusted Source SpringerLink SpringerLink provides researchers with access to millions of scientific documents from journals, books, series, protocols, reference works, and proceedings. View Source .

A significant percentage of sighted people with N24SWD also have a prior diagnosis of a mental health disorder such as major depression, bipolar disorder, obsessive-compulsive disorder, and schizophrenia or schizoid personality. For these individuals, N24SWD may have developed as a result of social isolation and other side effects of their disorder. Researchers suspect that N24SWD may sometimes develop naturally in people as a side effect of staying up late for many years and getting too much nighttime exposure to light.

In some cases, non-24-hour sleep-wake disorder in sighted people may be linked to a traumatic brain injury. Damage to cells in the retina Trusted Source National Library of Medicine, Biotech Information The National Center for Biotechnology Information advances science and health by providing access to biomedical and genomic information. View Source , to the pathway linking the retina and the SCN, to the pathway that regulates melatonin secretion, or to the SCN itself may disrupt or weaken the body clock.

Can Non-24-Hour Sleep-Wake Disorder Be Treated?

Though non-24-hour sleep-wake disorder is assumed to be a lifelong condition, certain treatments can help restore a 24-hour rhythm. Accompanying symptoms such as daytime sleepiness tend to resolve once the individual adapts to a routine that is synchronized with the social day and night. However, an individual’s body clock will generally become desynchronized again once they stop these therapies.

Non-24-hour sleep-wake disorder is commonly treated with melatonin supplements or the FDA-approved melatonin receptor agonist, tasimelteon. Trusted Source National Institutes of Health (NIH) The NIH, a part of the U.S. Department of Health and Human Services, is the nation’s medical research agency — making important discoveries that improve health and save lives. View Source Taken at a specified hour before the desired bedtime, these substances help prepare the body for sleep at the same time every night.

Using bright light therapy in the morning may also be an option for N24SWD in sighted people.

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