Awake women in bed/sleep disorder

Do you have trouble getting to sleep? Do you wake up during the night for no apparent reason? Wake up too early and can’t get back to sleep? You may have a circadian rhythm disorder. There are several:

  • Delayed sleep phase disorder
    • Can’t sleep when you go to bed, then sleep way past what’s considered a normal sleep cycle, even into the afternoon.
  • Advanced sleep phase disorder
    • Go to sleep early in the evening, wake up sometime between 2 and 5 am.
  • Jet lag
    • Difficulty adjusting to a different time zone.
  • Shift work disorder
    • A rotating or night shift interferes with your usual sleep habits.
  • Irregular sleep-wake rhythm
    • Sleep cycle is undefined, may take naps throughout the day and night.
  • Non-24-hour sleep-wake syndrome (non-24)
    • Awake at night, sleepy during the day.

Non-24-hour sleep-wake syndrome (non-24)

If you suspect you have any of these sleep disorders, you may want to check in with your health care provider. I recently heard about the last one on the list and because it was new to me, decided to do a little research and write this blog post.

Non-24 is a fairly rare disorder, mostly found in people who are totally blind, but it can occur in sighted people as well. The most common symptoms are trouble falling asleep at night, trouble staying asleep at night, and trouble staying awake during the day. By the way, if you find yourself being unusually sleepy during the day, that can also be a symptom of sleep apnea.

Sleep and your master clock

As I mentioned, non-24 is a condition related to circadian rhythms. We’ve all got a roughly 24-hour master clock in our brains that helps regulate several things, such as body temperature, hormonal changes, and sleep/wake cycles.

Before the invention of mechanical clocks (turn of the 14th century), humans were able to regulate their lives around basic things such as light and food, says Dr. Tarek Eid, a sleep specialist at Southern Maine Health Care (SMHC).

Those are the two things that gave the brain its circadian clock, and since our earth rotates once every 24 hours it made sense for the brain to regulate itself around 24 hours.

Taret Eid, MD, Internal Medicine, Sleep Medicine, Critical Care Medicine, Pulmonary Disease, Southern Maine Health Care/MaineHealth

The circadian rhythm most people are familiar with is the one associated with darkness and light. The light triggers us to wake up and darkness triggers us to go to sleep. Cells in our retinas absorb the light and provide the information our master clock needs to regulate our sleep-wake cycle.

Non-24 is most common in people who are totally blind because they have zero light perception. If their master clock doesn’t get the information it needs, it can’t recognize whether it is day or night.

When that happens, the clock tries to manage the sleep-wake cycle using its own built-in timer, which usually runs slower than a typical 24 hour day. Eventually, one or more symptoms of non-24 may develop.

The types of symptoms will vary from person to person, as will the severity and the frequency of them. Vicki Preddy is a registered nurse educator with Vanda Pharmaceuticals, which manufactures a non-24 treatment. She recently gave a presentation about non-24 for The Iris Network, a Portland, Maine organization that provides services and support for people who are blind or visually impaired. In the presentation, Vicki mentioned that symptoms may come and go.

That’s because without light information, the master clock will continue to run using its own timing system causing it to naturally drift in and out of alignment with a 24 hour clock.

Vicki Preddy, Vanda Pharmaceuticals

Drifting in and out may not always be an issue, but it can become one, says Dr. Eid.

You may get to the point where you sleep during the day and are awake at night. That’s where it can become a problem. It depends on the person’s lifestyle and social interactions – whether they’re regimented in their wakeup time and so forth.

Dr. Eid


Because the symptoms of non-24 can come and go, it can be difficult to diagnose. Keeping a sleep log may provide useful information. Dr. Eid says at SMHC’s Center for Sleep Disorders they sometimes give people a smartwatch to help track their sleep patterns. Basically, whether they are awake during daylight hours and asleep when there is no light.

They take it home and keep it on for two weeks. We can see if their train of awake and sleep is matching or is shifting gradually every day or going back and forth. It gives us a pretty good idea about their circadian rhythm and if there is a problem. Then we can help them navigate how to get it back.


Some people will take a melatonin supplement an hour before their desired bedtime to get back on track. Melatonin is a naturally occurring hormone produced by the brain, but to be activated on its own, the brain needs to be able to perceive light.

At nighttime, what happens when we stop seeing the bright light is our brain goes into the dusk mode or the dim light and our brains start making melatonin. That signals a cascade of other hormones that help put us to sleep. If there is no perception of light that can’t happen, so we can take melatonin.

Dr. Eid

Melatonin supplements are not FDA approved, but they are easy to obtain and fairly inexpensive. There is also an FDA-approved prescription medication available. It is a melatonin receptor agonist called Hetlioz or tasimelteon, manufactured by the company Vicki represents. Unfortunately, while it may provide relief, it is considered prohibitively expensive.

Non-24 in a sighted person

I’ve talked primarily about non-24 in people who are either totally blind or have limited light perception. The condition can also occur in sighted people, although rarely.

It’s typically in the people who have what we call a delayed sleep phase disorder. For instance, if you stay up late at night time when you’re supposed to go to sleep because you have to get up early, and then you start pushing yourself further one way or the other. The next thing you know, your circadian clock is out of sync and now you’re into this free range or non-24 hour sleep wake rhythm disorder.

Dr. Eid

Whether the individual is totally blind or has sight, the main complaint that Dr. Eid hears with non-24 is that someone is either too sleepy when they should be awake or too awake when they should be sleepy. If that sounds like you, you might want to see a sleep specialist.