Non-24 Sleep-Wake Disorder (Non-24)

What is non-24 sleep-wake disorder?

Non-24 sleep-wake disorder, or non-24, is a disruption of the circadian rhythm. The majority of people have an internal clock, or circadian rhythm, that runs in a 24-hour cycle. When a person has non-24, his/her wake-sleep times stretch out over a longer period of time. In other words, their internal clocks fail to reset roughly every 24 hours. Picture the sleep-wake cycle as a loop, so with non-24, the loop gets longer and longer, and the person’s 24-hour clock extends to 25 or 26 hours, or longer. Approximately 65,000 to 95,000 people in the United States are reported to have non-24. It is most common in people who are blind and have no light perception.

What causes non-24?

For people who are blind and have no light perception, the body has no point of reference regarding day or night. Therefore, the body’s internal clock isn’t fixed on the 24-hour period. Alterations in light sensitivity is also known to cause non-24 among sighted people. Other causes include trauma to the brain, hormonal deficiencies, and abnormal brain development, in which the section of the brain that controls the circadian rhythm hasn’t properly formed.

How is non-24 diagnosed?

A sleep study is conducted before a diagnosis of non-24 is made. This study will show irregularities in the patient’s REM sleep if the condition is present. Blood work and other tests are done to confirm the sleep study’s findings.

Where can I find more information about non-24?

• National Sleep Foundation
• NIH
• National Organization for Rare Diseases (NORD)