Sleep Education

American Academy of Sleep Medicine 

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Non-24-Hour Sleep-Wake Rhythm – Overview & Risk Factors

Non-24-Hour Sleep-Wake Rhythm 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 Non-24-Hour Sleep-Wake Rhythm 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 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 have Non-24-Hour Sleep-Wake Rhythm are blind. Light is the major influence on resetting the brain’s clock.

As your sleep pattern drifts a little later every day, Non-24-Hour Sleep-Wake Rhythm 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 phase disorder. 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 phase disorder. 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 type. 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. 


Someone with Non-24-Hour Sleep-Wake Rhythm 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

Risk Factors

More than half of blind people have Non-24-Hour Sleep-Wake Rhythm. 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.

Some people who are not blind 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. Bad 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 phase disorder.

People may also have this problem if they have neurological or brain disorders such as these:
  • Mental retardation
  • Brain injury
  • Dementia
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