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The non-24 hour sleep-wake disorder happens when the body’s rhythm does not adjust with the 24-hour synchronization of the daily cycle and affects our circadian rhythm. By type, it is a chronic circadian rhythm sleep disorder that interferes with sleep. It was previously known as a free-running circadian rhythm sleep disorder, and it is defined by chronic compromisation of the circadian rhythm. When an individual has this disorder, their daily cycle consists of 25-28 hours instead of the standard 24-hours. The extended time of the regular cycle happens gradually, making wake and sleep times happen later and later, which creates problems with your daily life, school, work, and social life. Every day the sleep-wake cycle of a person moves around the clock and eventually returns to the normal cycle for one or two days before continuing to move around again. This is why it is also called the free-running sleep disorder.
There are some rare cases where the disorder makes the daily cycle shorter than 24 hours, which creates earlier wake and sleep times but interferes with your daily life the same way. Whether the disorder creates a longer or shorter daily cycle, it causes insomnia, chronic sleep deprivation, fragmented sleep, grogginess, fatigue, and non-refreshing sleep. With the disorder, the circadian rhythm reacts to light exposure and sometimes social cues, hormone levels oscillations, and temperature fluctuations. In situations when people with this disorder are allowed to sleep in accordance with their cycle, they will not experience fatigue, but the fatigue can remain with regular sleep.
Circadian Rhythm Sleep Disorders
The non-24 hours sleep-wake disorder belongs to a group of sleep disorders that interfere with the timing of your sleep and affects your sleep quality. These circadian rhythm sleep disorders (CRSD) make it difficult for you to control when and where you fall asleep – you can easily be awake the entire night and fall asleep at work. You are getting the same sleep quality but your total sleep time is reduced. If you have another sleep disorder or medical condition that affects your sleep, then your sleep quality can be worse.
Individuals with a circadian rhythm can be two types of chronotypes – morning people or night owls. A chronotype is defined as a disposition that permits the person to sleep at a specific time in a period of 24-hours. Morning people are chronotypes that prefer waking up early and going to bed early, while night owls are chronotypes that stay up late and end up waking late as well. However, both chronotypes possess a normal circadian rhythm because their circadian rhythms involve falling asleep and waking up at the same time each day, along with an adjustment period when they change their routine.
Among the symptoms you can experience are waking up late, bedtimes that slowly star later, insomnia, difficulty falling asleep when it is bedtime and having a restful sleep, history of delayed sleep patterns, excessive daytime sleepiness, and depression. It can also include apraxia (a motor disorder that causes difficulties with performing tasks or movements when asked) nausea, cognitive dysfunction, impaired balance, joint pain, diarrhea, photosensitivity, and hair loss.
The non-24 sleep-wake disorder can occur in two types of cases – sighted and blind.
For people that have the disorder, their bodies and circadian rhythms insisted that both the day and night are longer (or in some cases shorter) than 24 hours. The circadian rhythms refuse to adjust to the light-dark cycle, making it difficult to sleep at regular times and causing daily shifts in all circadian rhythm aspects like metabolism, body temperature, hormone secretion, and alertness time. People with this disorder have difficulty adjusting to the regular sleep-wake cycles and any changes to it like medication, illnesses, traveling to different time zones, daylight saving time, different seasons and growth spurts. When trying to adjust, they often experience stress, lower sleep propensity, and sleep deprivation.
The disorder can occur at any age, but it is common for it to develop in in adulthood and to come after a delayed sleep phase disorder. Most individuals that have this disorder have difficulty functioning correctly with school, work, and social life because they are unable to perform in scheduled daily activities that happen in the normal 24-hour cycle. Attempts of adjusting usually end with insomnia, excessive sleepiness, chronic sleep deprivation, and with severe physical and psychological symptoms – depression, headaches, fatigue, decreased appetite and sleepiness.
More than half of the people who have non-24 hour sleep-wake disorder are entirely blind. Same as for sighted people, it can happen at any age from birth to adulthood. It usually occurs after the loss of a person’s eyes or sight. It happens because of the lack of photosensitive ganglion cells in the retina, without whom the hypothalamus gets no cue to synchronize the circadian rhythm to the daily 24-hour cycle. Impaired patients who have some light perception rarely experience this disorder because their hypothalamus is getting those cues in a small amount and can trigger the proper 24-hour cycle. Even the minimal amount of light exposure affects the body’s clock.
The non-24 hour sleep-wake disorder is primarily a neurological condition, so the primary cause of it is abnormalities of the suprachiasmatic nucleus which is the part of the brain that is responsible for the body’s clock and rhythm. Typically, external cues like light exposure are what helps the body maintain its 24-hour cycle. In cases where the body’s cycle moves away from the 24-hour cycle, the external cues are what help align it back to the previous rhythm. This way the body keeps its 24-hour cycle even with natural interruptions that happen with illness, daylight saving, travel, insomnia or season changes.
For sighted people, this disorder is sporadic, but not uncommon. Some of the cases involved a head injury or a neurological issue prior to the development of the disorder. As we mentioned before, in the majority of cases, the disorder is linked to the abnormal functioning of the hypothalamus, specifically, the part called the suprachiasmatic nucleus (SCN) that is in charge of perceiving these cues. Simply put, the retina or the brain are not reacting properly to light, and the body is not getting proper signals. A 2002 study done by Okawa and Uchiyama researched this disorder and found that the sleep-wake cycle lasted for 25.12 hours on average. They also found that the minimum core body temperature is triggered much earlier than usual (which is two hours before awakening), which can interfere with the body’s ability to perceive light and possibly be a trigger for the disorder.
In other cases, among the cause of the disorder are isolated from natural light, unusual levels of natural hormones like melatonin, unusual responses to light exposure, depression or other disorders like bipolar disorder or delayed sleep phase disorder.
The disorder occurs more frequently in completely blind people because of their inability to perceive light. Their bodies are not able to use light exposure as a way to keep a healthy 24-hour daily cycle. When their circadian rhythm changes, they cannot renew a 24-hour cycle by themselves and without any medical help.
The non-24 hour sleep-wake disorder is very rare, and it is not yet sure how many people have it. The most significant risk factor is a neurological condition or issue that severely impacts the brain’s ability to perceive light. The majority of people who have this disorder are completely blind because they are unable to see light which plays a crucial role in maintaining a circadian cycle. Of course, not everybody who is blind will have this disorder, and it is also present with people who are not blind. What is consistent about this disorder is that people who have difficulties perceive light are at risk of developing the non-24 hour sleep-wake rhythm disorder.
Individuals with neurological conditions and mental illnesses such as dementia, Alzheimer’s disease, brain damage, or mental retardation by default have a weak body clock, which puts them at risk of developing the non-24 hour sleep-wake rhythm disorder. Of course, having these conditions will not always result in these individuals having this disorder, it is just easier for them to develop it. Along with that, bad sleep habits also put us at risk of having this disorder, especially in combination with not getting proper exposure to daily light. It has also been reported to appear with behavior issues like substance abuse and with those who are taking treatment for the delayed sleep phase disorder.
How Common is Non-24 Hour Sleep-Wake Disorder?
As we mentioned before, this disorder is not common. Among those who develop the disorder, blind people are the most common. Approximately 55 to 70 percent of individuals who are entirely blind have this disorder because they don’t receive light information that regulates the 24-hour day-night cycle in our bodies. In cases involving sighted people, the number is not known, but the majority of these reported cases involved a history of delayed circadian patterns that result in any circadian rhythm disorder, including the non-24 hour sleep-wake disorder.
The non-24-hour sleep-wake disorder can be diagnosed if the patient has troubles following a 24-hour light-dark cycle. To diagnose this issue doctors look at the symptoms a patient reports, medical history, and sleep patterns seen through a sleep diary. Unlike other circadian rhythm sleep-wake disorders, this one requires documentation of gradual shifting of the sleep-wake times. The best way to do that is to use an actigraphy to watch sleep-wake cycles. Actigraphy is used to measure movement during sleep. The sensors can be put anywhere, but a small instrument called actigraph is usually worn on the wrist or ankle for at least one week to record the person’s motor activity accurately. In some instances, melatonin levels can be evaluated with lab tests to show if there are hormones rises and falls during the day and night.
Like all sleep-wake disorders that affect the circadian rhythm, the treatments for the non-24 hour sleep-wake disorder are light and melatonin therapy. These treatments can successfully put the circadian rhythm back to 24 hours for sighted individuals. But for these treatments to work, they need to be continued along with the maintenance of consistent wake and sleep times. If these treatments are discontinued, the delayed pattern of the circadian rhythm returns.
Light therapy involves using artificial light that helps control sleep. In the treatment, the person is exposed to full-spectrum light – bright light consisting of thousands of lux of white and blue light. This light is emitted from a lightbox, and it is supposed to mimic sunlight and gives the body proper exposure to daily light, or rather, its replacement. Apart from helping synchronize a specific schedule and sleep, the treatment has also had great results for treating night shift workers to help them experience night as day. For people with blindness, the most common treatment is timed melatonin therapy. The treatment with melatonin supplements can help promote regular circadian rhythms and sleep patterns.