neurologic disorders
Circadian Rhythm Sleep Disorders
Circadian rhythm sleep disorder, altered sleep phase types
In these syndromes, patients have normal sleep quality and duration with a 24-hour circadian rhythm cycle, but the cycle is out of sync with desired or necessary wake times. Less commonly, the cycle is not 24 hours, and patients awaken and sleep earlier or later each day. If able to follow their natural cycle, patients have no symptoms. Delayed sleep phase syndrome:Patients consistently go to sleep and awaken late (eg, 3 AM and 10 AM). This pattern is more common during adolescence. If required to awaken earlier for work or school, excessive daytime sleepiness results; patients often present because school performance is poor or they miss morning classes. They can be distinguished from people who stay up late by choice because they cannot fall asleep earlier even if they try. Mild phase delay (<3 hours) is treated by progressive earlier arising plus morning bright light therapy, perhaps withmelatonin4 to 5 hours before the desired bedtime. An alternative method is to progressively delay bedtime and awakening time by 1 to 3 hours/day until the correct sleep and wake times are reached. Advanced sleep phase syndrome:This syndrome (early to bed and early to rise) is more common among older people and responds to treatment with bright light in the evening and light-preventing goggles in the morning. Non–24-hour sleep-wake syndrome:Much less common, this syndrome is characterized by a free-running sleep-wake rhythm. The sleep-wake cycle commonly remains constant in length but is>24 hours, resulting in a delay of sleep and wake times by 1 to 2 hours each day. This disorder is more common among blind people.Tasimelteon, amelatoninreceptor agonist, can increase nighttime sleep duration and decrease daytime sleep duration in totally blind patients who have this disorder. The dose is 20 mg orally once a day before bedtime, at the same time every night. 