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Non-24-hour Sleep-Wake Disorder

Non-24-hour sleep-wake disorder is one of six circadian rhythm disorders and is common in people with total blindness.

Most have heard of the circadian rhythm, the 24-hour cycle our body uses to time sleep, appetite, energy level, and more. The circadian rhythm is controlled by a master clock in the brain called the suprachiasmatic nucleus (SNC). The SCN uses cues from ambient light and other time indicators to keep us synchronized with a 24-hour rhythm, such as releasing the sleep hormone, melatonin, when it gets dark.

With non-24-hour sleep-wake disorder, the body clock becomes desynchronized from our environment.

What is Non-24-hour Sleep-Wake Disorder?

Non-24-hour sleep-wake disorder, formerly called free-running rhythm disorder or hypernychthemeral syndrome, is a condition in which the body clock is out-of-sync with the environment and the circadian rhythm is shorter or, more often, longer than 24 hours.

Over time, this pushes sleep and wake times progressively earlier or later, leading an individual to become desynchronized with regular daylight hours and experience inappropriate fluctuations in appetite, mood, and alertness. Sleep and wake times may catch up to desired hours temporarily but will continue to drift, or cycle, away from this. Maintaining a regular sleep cycle is incredibly challenging for individuals with non-24-hour sleep-wake disorder and, over time, this may adversely affect one’s health and ability to keep personal and professional commitments.

It’s estimated that about 50% of people with total blindness have non-24-hour sleep-wake disorder due to the lack of light input to the brain. Sighted people can also be affected by the condition and are often misdiagnosed with another sleep condition. According to the Sleep Foundation, the cause of non-24-hour sleep-wake disorder in sighted people is unclear, but researchers suspect it may have a genetic component or may “develop naturally in people with a weak circadian clock as a side effect of staying up late for many years and getting too much nighttime exposure to light.” In some cases, the condition can also be linked to a traumatic brain injury.


Non-24-hour sleep-wake disorder is believed to be a lifelong condition, but treatment can restore and help to maintain a 24-hour rhythm. For individuals with blindness, this condition is commonly treated with melatonin supplements or the FDA-approved melatonin receptor agonist, tasimelteon. For sighted people with this condition, bright light therapy paired with melatonin supplements may be used. A sleep physician can help determine the best timing to begin bright light therapy.

The first step on the path to safe and restful sleep is to schedule an appointment with your doctor or sleep specialist. A sleep specialist is able to take a comprehensive and individualized approach to treating your sleep disorder head-on. Non-24-hour sleep-wake disorder doesn’t have to disrupt your life.

Schedule your first appointment today by clicking here.