Home » Sleep Disorders » Non-24-Hour Sleep-Wake Rhythm
December 2020 |  Reviewed by:  Virginia Skiba, MD and Reeba Mathew, MD

What is non-24-hour sleep-wake rhythm disorder?

Non-24-hour sleep-wake rhythm disorder (N24SWD) is one of several circadian rhythm disorders. People with these disorders have sleep times that seem to be out of alignment. Their sleep patterns do not follow the “normal” sleep times at night.

The sleep time of people who have N24SWD shifts a little later every day. Sleep time and wake up time continue to move later and later every day. Sleep times go in and out of alignment with other people as weeks go by.

Normal people have a circadian rhythm that is slightly longer than 24 hours. Every day, morning light and other behaviors reset the sleep-wake clock to a 24-hour schedule. Without light and this clock resetting, people’s sleep time will drift later and later. This is why many people who are blind have N24SWD. Light is the major influence on resetting the brain’s clock.

As your sleep pattern drifts a little later every day, N24SWD can be confused with other circadian rhythm disorders. As sleep time drifts later, you do not fall asleep until morning. It may seem like you have delayed sleep-wake phase. After days of later and later bedtime, you are sleeping during the day. After more days, you begin to sleep in the early afternoon and evening. This makes it look like you have advanced sleep-wake phase. After more days, you are back to sleeping during normal night hours. Then the drifting sleep time continues around the clock again. The sleep time is not broken up into pieces as with irregular sleep-wake rhythm. The sleep time is only broken if there are outside disturbances. Your main sleep time does not occur at the same time every day. It continues to get later and later every day.

What are symptoms of non-24-hour sleep-wake rhythm disorder?

Someone with N24SWD may:

  • Have a sleep cycle that seems to get later and later every night
  • Wake up later and later every day
  • Have a sleep time that sometimes seems to jump around
  • Have their sleep cycle drift later and later without any outside interruptions

What are risk factors for non-24-hour sleep-wake rhythm disorder?

More than half of blind people have N24SWD. Yet some blind people do not have this disorder. They still have a working brain pathway to the part of the brain that functions as the body clock. Also, some blind people still have a normal circadian rhythm. Their clocks can be reset to other time cues besides light. But the majority of blind people report some kind of sleep disturbances.

People who are not blind can also have this disorder, but these cases are very rare. There are conditions that may make it easier for this problem to occur. Daily light and other activities are important in resetting our sleep clocks. Certain sleep habits may allow this condition to occur in people who have weaker clocks. This is especially true when they do not get proper exposure to daily light. If you never left a dark room, your circadian clock may not reset. Your sleep time could drift later and later. Your body would not have the normal time cues from your surroundings.

Some people with this problem may have or may develop psychiatric or personality disorders. This disorder may also be seen with other behaviors such as substance abuse.

This problem has also been reported in people who are being treated for delayed sleep-wake phase.

People may also have this problem if they have neurological or brain disorders such as:

  • Mental disability
  • Brain injury
  • Dementia

How to diagnose non-24-hour sleep-wake rhythm disorder?

If you think you have N24SWD, you should talk to your medical provider. This disorder causes problems with work and family. Your sleep cycle gradually moves in and out of normal sleep times. There is not one fixed sleep time, either early or late. Sometimes the main sleep time is during the night and sometimes it is during the day.

People with this disorder have trouble maintaining relationships and fulfilling responsibilities. This disorder may make you homebound and isolated. Being homebound can make this problem worse. Some people also try behaviors or medicines to correct the problem. This may only worsen the condition. They may get into trouble if they try to fix this problem on their own by taking pills or alcohol.

Your doctor may ask you about your medical, neurological, and sleep symptoms. Your doctor may also ask you about your medication and alcohol use, and your family history. Be sure to inform your doctor of any past or present drug, alcohol, and medication use. Also tell your doctor if you have ever had any other sleep or neurological disorders.

Your doctor should do a thorough medical and neurological exam.

You will be asked to complete a sleep diary to record your natural sleep and wake up times over several weeks. You may be asked to rate your sleep with a simple questionnaire.

The diagnosis of N24SWD is made clinically and with the use of the sleep diary. An additional testing method called actigraphy may be required. Actigraphy involves a device that records inactive and active episodes over a period of one to two weeks. Typically, the device looks like a wristwatch, and you wear it day and night.

Other testing methods to measure body temperature or melatonin levels may be used. Most often these methods are used for the purpose of research.

Your doctor may suspect that a neurological or other medical problem is involved. In this case, you may be asked to have your blood tested. You may also need a CT scan or an MRI.

A sleep study is usually not needed to detect this disorder. You may need to do a sleep study if you are at risk for other sleep disorders. The sleep study is called polysomnography. It charts your brain waves, heartbeat, muscle activity, and breathing as you sleep. It also records how your arms and legs move. This shows if there are other sleep disorders that are causing or increasing your sleep problems. Examples include sleep apnea and periodic limb movement disorder. A sleep study is not used to make the diagnosis of N24SWD.

How to treat non-24-hour sleep-wake rhythm disorder?

Treatment for N24SWD is aimed at trying to increase stimulation to reset the sleep clock in the brain. The goal is to have one long sleep time at night and one long awake time during the day.

Timed melatonin is one possible treatment for blind adults. Patients should work with their sleep doctor to determine the proper time and dosage of melatonin.

For sighted people, light treatment is a way to help a weakened body clock. Other scheduled behaviors can also help.

There is a medication that is FDA-approved for this condition, called tasimelteon (Hetlioz). Talk to your doctor more about this and other options.

Education and behavioral counseling can be helpful. Following the rules of good sleep hygiene will help you keep a regular bedtime. As research continues, more information will become available about the causes and other future treatments of this uncommon sleep disorder.

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