Non-24-Hour Sleep-Wake Syndrome in Sighted and Blind Patients

Non-24-hour sleep-wake syndrome is a cyclic debilitating circadian rhythm sleep disorder characterized by an inability to sleep on a 24-hour schedule. Individuals who are physically or biologically isolated from a normal 24-hour light/dark cycle exhibit a sleep/wake cycle that is different from, and usually longer than, 24 hours. It is relatively rare in sighted patients and in some cases may be associated with delayed sleep phase disorder or psychiatric disorders. It is more common in individuals who are totally blind. This article reviews the clinical characteristics of patients who have non-24-hour sleep-wake syndrome, discusses the biologic mechanisms that may underlie its development, and describes potential treatment strategies.