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Circadian rhythm sleep disorders are caused by desynchronization between internal sleep-wake rhythms and the light-darkness cycle. Patients typically have insomnia, excessive daytime sleepiness, or both, which typically resolve as the body clock realigns itself. Diagnosis is clinical. Treatment depends on the cause.

In circadian rhythm disorders, endogenous sleep-wake rhythms (body clock) and the external light-darkness cycle become misaligned (desynchronized). The cause may be internal (eg, delayed or advanced sleep phase syndrome) or external (eg, jet lag, shift work).

If the cause is external, the timing of other circadian body rhythms, including temperature and hormone secretion, is altered; in addition to insomnia and sleepiness, these alterations may cause nausea, malaise, irritability, and depression. Risk of cardiovascular disorders may also be increased.

Repetitive circadian shifts (eg, due to frequent long-distance travel or rotating shift work) are particularly difficult to adapt to, especially when the shifts change in a counterclockwise direction. Counterclockwise shifts are those that shift awakening and sleeping times earlier (eg, when flying eastward or when rotating shifts from days to nights to evenings). Symptoms resolve over several days or, in some patients (eg, the elderly), over a few weeks or months, as rhythms readjust. Because light is the strongest synchronizer of circadian rhythms, exposure to bright light (sunlight or artificial light of 5,000 to 10,000 lux intensity) after desired awakening time speeds readjustment. Melatonin given in the evening may be tried (see Sleep and Wakefulness Disorders: Other sedatives).

Patients with circadian rhythm disorders often misuse alcohol, hypnotics, and stimulants.

Circadian rhythm disorders include the following.

Circadian rhythm sleep disorder, jet lag type (jeg lag disorder): This syndrome is caused by rapid travel across > 2 time zones. Eastward travel (advancing the sleep cycle) causes more severe symptoms than westward travel (delaying sleep).

If possible, travelers should gradually shift their sleep-wake schedule before travel to approximate that of their destination and maximize exposure to daylight (particularly in the morning) in the new locale. Short-acting hypnotics or wake-promoting drugs (eg, modafinilSome Trade Names
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Circadian rhythm sleep disorder, shift work type (shift work disorder): Severity of symptoms is proportional to the frequency of shift changes, the magnitude of each change, and the frequency of counterclockwise (sleep advancing) changes. Fixed-shift work (ie, full-time night or evening) is preferable; rotating shifts should go clockwise (ie, day to evening to night). However, even fixed-shift workers have difficulties because daytime noise and light interfere with sleep quality, and workers often shorten sleep times to participate in social or family events.

Shift workers should maximize their exposure to bright light (sunlight or, for night workers, especially constructed bright artificial lightboxes) at times when they should be awake and ensure that the bedroom is as dark and quiet as possible during sleep. Sleep masks and white-noise devices are helpful. When symptoms persist and interfere with functioning, judicious use of hypnotics with a short half-life and wake-promoting drugs is appropriate.

Circadian rhythm sleep disorder, altered sleep phase types: In these syndromes, patients have normal sleep quality and duration with a 24-h circadian rhythm cycle, but the cycle is out of synch with desired or necessary wake times. Less commonly, the cycle is not 24 h, 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 h) is treated by progressive earlier arising plus morning bright light therapy, perhaps with melatonin 1 h before the desired bedtime. An alternative method is to progressively delay bedtime and awakening time by 3 h/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 the elderly and responds to treatment with bright light in the evening and light-preventing goggles in the morning.
• Non–24-h 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 h, resulting in a delay of sleep and wake times by 1 to 2 h each day. This disorder is more common among blind people.

Last full review/revision April 2008 by Karl Doghramji, MD

Content last modified April 2008