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, other circadian body rhythms, including temperature and hormone secretion, can become out of sync with the light-darkness cycle (external desynchronization) and with one another (internal desynchronization); in addition to insomnia and excessive sleepiness, these alterations may cause nausea, malaise, irritability, and depression. Risk of cardiovascular and metabolic 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, 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 a strong synchronizer of circadian rhythms, exposure to bright light (sunlight or artificial light of 5,000 to 10,000 lux intensity) after the desired awakening time and the use of sunglasses to decrease light exposure before the desired bedtime speed readjustment. Melatonin given in the evening may help (see 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 (jet 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 after arriving in the new locale, they should maximize exposure to daylight (particularly in the morning) during the day and exposure to darkness before bedtime. Short-acting hypnotics and/or wake-promoting drugs (eg, modafinil) may be used for brief periods after arrival.
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, the number of consecutive nights worked, the length of shifts, 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, specially 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. Wearing sunglasses during the morning commute home in anticipation of sleep is also useful. 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 sync 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.
Last full review/revision November 2012 by Karl Doghramji, MD
Content last modified May 2013