Circadian Rhythm Sleep Disorder

Circadian rhythm sleep disorder is a persistent or recurrent pattern of sleep disruption characterized by excessive sleepiness or insomnia. These symptoms result from a mismatch between the individual's sleep-wake schedule and endogenous circadian rhythms. To meet the criteria for this disorder, an individual must demonstrate significant distress or impairment and not have symptoms exclusively during the course of another sleep or mental disorder.

Several subtypes of circadian rhythm sleep disorder have been described. In the delayed sleep phase type, the individual maintains later sleep-wake hours than are socially acceptable and is unable to awaken in time to meet social or occupational responsibilities in the morning. In the jet lag type, the individual has a mismatch of the sleep-wake schedule and circadian rhythms caused by transmeridian travel.

In the shift work type, the individual reports symptoms related to work at unusual times of day and night, often in conjunction with changing work and sleep schedules. Advanced sleep phase syndrome presents with symptoms opposite those of delayed sleep phase syndrome: affected individuals fall asleep early in the evening and awaken earlier than desired in the morning. Recent studies have identified three kindreds with a familial form of advanced sleep phase syndrome, which appears to be inherited as an autosomal dominant trait (Jones et al. 1999). Although circadian rhythms normally have a period of approximately 24.2 hours, most individuals easily entrain to the 24-hour light-dark cycle. Individuals with non-24-hour sleep-wake pattern are unable to entrain their circadian rhythms (including the sleep-wake rhythm) to the 24-hour day and follow the pattern of their endogenous rhythms with a period of just over 24 hours. This results in cyclic symptoms of sleep-onset insomnia, difficulty awakening, daytime sleepiness, and early-morning awakening as the individual's rhythms cycle in and out of synchrony with the 24-hour day. This pattern has been observed most commonly in blind individuals, particularly those with no light perception (Lockley et al. 1997; Sack et al. 1992).

Behavioral/psychotherapeutic treatment Chronotherapy is the only behavioral treatment that has received research attention in the management of delayed sleep phase syndrome. Results from case studies (Czeisler et al. 1981) suggest that chronotherapy may be useful for selected patients in shifting the timing of sleep from suboptimal hours to more appropriate times to meet occupational and social responsibilities and needs. In clinical practice, however, there is a great deal of variability in patients' acceptance and compliance with this procedure. A simpler and often more effective procedure involves strict adherence to an early and regular rising time.

The management of other circadian rhythm sleep disorders, such as jet lag and shift work types, involves preventive, environmental, and rescheduling measures (Monk 1994). For example, the effect of jet lag on sleep and alertness may be minimized by gradually changing one's schedule before traveling across time zones. By staying up later at night or arising earlier in the morning, the traveling individual will adjust his or her circadian rhythm to the clock time of the intended destination. For shift work, attention also needs to be paid to scheduling factors, as well as to environmental factors (e.g., telephones, doorbells, street noises) that may disrupt sleep during the day.