How Circadian Rhythms Can Get Off-Beat for the Blind

by Rachel Pulver

A person concealing their face with a distorted, undulating clock.

It may feel like time is warping around you. You wake up from sleep and you feel like it is two o’clock in the afternoon, but it is actually eight o’clock in the morning. Your body’s perception of time is not at all lined up with the day. This is a sign that you may be suffering from Non-24-Hour-Sleep-Wake Disorder.

What is Non-24-Sleep-Wake Disorder?

Non-24 is a circadian rhythm disorder that disrupts the natural timing mechanism in your body, which is colloquially referenced as your internal body clock and scientifically known as your master body clock. The body clock runs on a 24-hour schedule, which marks the release of signals from your brain that trigger your circadian rhythm to fulfill crucial tasks such as the hormones that manage your sleep-wake-cycle, body temperature, and appetite. In nature, circadian rhythm can be observed when flowers open up and when nocturnal animals come out at night.

Sometimes our master body clocks can run a little longer than 24 hours, thus, continually rolling over the minutes to the next tomorrow until our natural rhythms are no longer synced up to the 24-hour-day-night-cycle. It is important that our body stays on its rhythms of a 24-hour cycle, so our body can be productive during the day and slow down at night to rest and recover. But there comes an issue. Taken from

Light perception is a key element in maintaining a 24-hour body clock because environmental light signals the time of day to the brain. In people who are sighted, this resets the body clock to 24 hours, ensuring that the circadian rhythms synchronize to the typical day-night cycle. For people who are totally blind, there are no such light cues, and the body clock’s extra minutes add up day by day until the circadian rhythms are essentially upside down from a typical 24-hour day

An estimated 50% to 70% of blind individuals who do not have light perception are affected by Non-24-Sleep-Wake-Disorder.

A study conducted in France showed how important light cues are to the body in order to maintain a consistent internal clock. Participants lived in dark caves, completely void of light cues and clocks for 40 days. As a result, participants started to experience a shift in their natural rhythms whereby their bodies adopted a 32-hour body clock instead of a 24-hour body clock. Even though they were in the cave for 40 days, to them it felt like 29 days. The lack of light cues distorted their natural sleep-wake-cycle. Clot, a participant of the study reported that people had varying body rhythms that had people eating and sleeping at odd times from one another. This study shows the validity of just how pivotal light cues play for the body in maintaining a healthy circadian rhythm.


What are the Symptoms of Non-24?

  • Inability to sleep at night or stay asleep.
  • A powerful urge to sleep during the day.
  • Trouble falling asleep.
  • The times you want to sleep seem to constantly shift.
  • Wake up groggy or not feeling like you have slept.
  • Sleeping during the day.
  • Unexpectedly falling asleep during the day.
  • Difficult to function at work/school.
  • Hard to concentrate.
  • Irritable due to lack of sleep.
  • Fight to stay awake during the day.
  • Battling between sleep and exhaustion.

Treating Non-24

If you related to this article and would like to seek medical knowledge on Non-24-Sleep-Wake-Disorder, you can call a specialized health educator at 1-855-856-2424 who will answer all your questions and help assist you in communicating with your doctors about your Non-24.