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What is Non-24?

Non-24 is a circadian rhythm disorder

Lucia, age 28: "I used to lie in bed not able to sleep, and then I'd get in trouble at school for falling asleep in class."

  • Do you have a hard time sleeping through the night?
  • Do you find you have a strong urge to nap during the day?
  • Is it hard for you to concentrate?
  • Are you feeling restless, overtired, or frustrated?
  • Do you feel your sleep patterns are different from those around you?
  • Does it seem like you're the only person who's experiencing these things?

If your answer to any of these questions is yes and you're totally blind, you may have Non-24-Hour Disorder (Non-24).

Non-24 is a circadian rhythm disorder. Your circadian rhythms are controlled by your master body clock and tell you when to sleep, when to wake, when to eat, among other things.

In most people, the master body clock runs slightly longer than 24 hours. What this means is that rather than cycle on a 24-hour day, most people's natural rhythms actually cycle a bit longer. Whether the cycle runs two minutes or 30 minutes longer, if you have Non-24 these minutes add up day after day, a few one day adding to a few more the next, eventually causing a noticeable change in the times during the day when your body expects to sleep and expects to be awake.

Though Non-24 may appear to be a sleep disorder, it isn't. It's actually a serious, chronic circadian rhythm disorder very common in people who are totally blind, and it can arise at any age. Currently, there are 1.3 million people who are legally blind in the United States. Of the legally blind, 130,000 have no light perception (i.e., totally blind), and as many as 70% suffer from the effects of living with Non-24.

Difficulty at night and challenges during the day

Non-24 brings about two significant symptoms.

First is a profound inability to sleep or to stay asleep at night, and the second is an overwhelming urge to sleep during the day. Both changes are caused by the timing of the release of the hormones, melatonin and cortisol. Melatonin controls sleep and mood, and cortisol controls when to wake up and when to eat. Cortisol also controls your metabolism, cardiovascular function, immune system, and appetite. Because the release of melatonin and cortisol shifts continually, not all nights are the same. Some are sleepless, others are normal, and poor sleep happens only when the master body clock is out of sync with the typical day-night cycle. And when poor sleep happens, sleep deprivation may make it difficult to focus on the task at hand and may affect your mood when interacting with family, friends, and colleagues.

Non-24 comes about when the master body clock runs on its own natural rhythm. Hence the name, Non-24, which indicates a master body clock that is not 24 hours long. For unknown reasons, most people's body clock runs a little longer than 24 hours, which means most people could have Non-24 to some degree. The difference is that for sighted people, environmental light cues signal the brain to reset the master body clock every day to 24 hours.

For people who are totally blind, the master body clock runs its natural course. This means that if your body clock runs on a 24.5-hour schedule, today you're 30 minutes behind and tomorrow your body clock will be an hour behind. The next day will be 90 minutes, and so on. Day by day, this time adds up until you're many hours behind, creating a rhythm that's out of sync with the typical day-night cycle. Eventually, your body operates as if night is day and day is night. While you could try to maintain your usual schedule, more often than not you have a hard time sleeping at night and then feel an overwhelming urge to sleep during the day. In time, you once again reach the point when your body clock is in sync with the typical day-night cycle. But then, just as quickly, it moves out of sync again.

A complication that can sap your energy

Because its effects are so wide-ranging, Non-24 may hinder the methods you use to get through the day. It may sap your energy. You may suddenly fall asleep at inopportune times, and it may make crucial daily tasks a challenge, such as counting bus stops so you know when to get off.

Living with Non-24 may make you feel as though no one understands what you're going through, and this sense of being alone only makes the effects feel that much worse. The truth is, you're not alone. There are many other people living with Non-24 who are experiencing many of the same challenges you do. Using the information on this website, as well as talking to others, may help guide you as you manage Non-24 in your own life.

Step 1 on your road to the help you need? Read the next section of this website to get a better understanding of the master body clock and circadian rhythms and how they may be affecting your life.