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.

It is also important to keep sleep episodes and mealtimes scheduled at regular times. Sleep disturbances may be minimized by keeping the same schedule on days on and off work, although family and social obligations often make this recommendation impractical. Because the duration of a sleep episode is dependent on the actual bedtime, the night shift worker should begin his or her sleep period as early as possible in the morning. Because it may be difficult to sleep for more than 4 or 5 hours continuously during the day, it may be necessary to plan two separate sleep episodes, including a nap in the evening, in order to stay alert the next night. Rotating shifts that move from days to evenings to nights are easier to adapt to than shifts that rotate in a counterclockwise direction. To facilitate circadian adaptation, rapid (every 2-3 days) or very long (about 3 weeks) shift rotations have been recommended.

Somatic treatments In addition to behavioral treatments, somatic treatment is often used for circadian rhythm sleep disorder. In particular, appropriately timed bright white light can shift endogenous circadian rhythms to more closely match the required environmental rhythms. Bright light in the evening hours clearly delays sleep onset with less consistent effects on Stage 3/4 sleep or REM sleep (Bunnell et al. 1992; Dijk et al. 1991). Evening bright light also causes rapid and dramatic shifts in the phase position of endogenous circadian rhythms, such as core body temperature. Conversely, bright light in the morning hours advances circadian rhythms, that is, causes core body temperature minima to occur at an earlier clock time. These effects of bright light have been reported to improve sleepiness during waking hours in patients with delayed sleep phase syndrome (Rosenthal et al. 1990), in those with insomnia with early-morning awakening (Lack and Wright 1993), and in volunteers on a simulated night shift (Dawson and Campbell 1991; Eastman et al. 1994, 1995). Effects on jet lag have been more variable (Boulos et al. 1995; Samel and Wegmann 1997). Exogenous melatonin may also help to shift abnormally entrained circadian rhythms to a more normal phase. Like bright light, melatonin shifts circadian rhythms in a time-dependent fashion, but its effects are almost opposite to those of light. Thus, evening administration of melatonin shifts circadian rhythms to an earlier time, and morning melatonin shifts rhythms to a later time (Lewy and Sack 1997). The efficacy of exogenous melatonin administered in the early evening hours has been shown in delayed sleep phase syndrome (Dagan et al. 1998; Dahlitz et al. 1991; Nagtegaal et al. 1998). Melatonin given later in the evening can help to entrain sleep-wake rhythms in blind individuals with non-24-hour sleep-wake pattern (Sack and Lewy 1997; Sack et al. 1991; Skene et al. 1999). Although some studies have indicated that melatonin also may be effective for treating the sleep disturbances accompanying jet lag and shift work (Arendt and Deacon 1997; Petrie et al. 1993), other studies have failed to demonstrate an effect (Spitzer et al. 1999).

Pharmacological treatment Other medications have a more limited role in the treatment of circadian rhythm sleep disorder. Several studies have reported the efficacy of short-acting benzodiazepine hypnotic medications in simulated night shift work, that is, sleep during daytime hours (Seidel et al. 1984; Walsh et al. 1984, 1988). In such cases, hypnotics are not expected to be used on a continuous basis, but rather only on the first 2 days of a particular night shift. In patients with delayed sleep phase syndrome, hypnotic medications may be useful in reinforcing a particular time of sleep onset. However, no empirical studies have been conducted to verify this. Short-acting benzodiazepine hypnotics can also ameliorate symptoms of jet lag (Lavie 1990).