CIRCADIAN RHYTHM SLEEP DISORDER, DELAYED SLEEP PHASE TYPE (Delayed Sleep Phase Disorder)

Circadian rhythm sleep disorder, delayed sleep phase type (DSP) is characterized by habitual sleep-wake times that are delayed, usually more than two hours, relative to conventional or socially acceptable times. Affected individuals complain of difficulty falling asleep at a socially acceptable time, but once sleep ensues, sleep is reported to be normal. A typical patient has difficulty initiating sleep and prefers late wake-up times. When allowed to follow his or her preferred schedule, the patient’s circadian phase of sleep is delayed but is relatively stable. Attempts to fall asleep earlier are usually unsuccessful.

CIRCADIAN RHYTHM SLEEP DISORDER, ADVANCED SLEEP PHASE TYPE (Advanced Sleep Phase Disorder)

Circadian rhythm sleep disorder, advanced sleep phase type (ASP), is a stable advance of the major sleep period characterized by habitual sleep onset and wake-up times that are several hours earlier relative to conventional and desired times. Affected individuals complain of sleepiness in the late afternoon or early evening, early sleep onset, and spontaneous early morning awakening. Individuals typically complain of early morning insomnia and excessive evening sleepiness. When patients are allowed to maintain an advanced schedule, their sleep is usually normal for age.

CIRCADIAN RHYTHM SLEEP DISORDER, IRREGULAR SLEEP-WAKE TYPE (Irregular Sleep-Wake Rhythm)

Circadian rhythm sleep disorder, irregular sleep-wake type, is characterized by lack of a clearly defined circadian rhythm of sleep and wake. The sleep-wake pattern is temporally disorganized so that sleep and wake periods are variable throughout the 24-hour period. Individuals have symptoms of insomnia and excessive sleepiness, depending on the time of day.

CIRCADIAN RHYTHM SLEEP DISORDER, FREE-RUNNING TYPE (Nonentrained Type)

Circadian rhythm sleep disorder, free-running type, (nonentrained type) is characterized by sleep symptoms that occur because the intrinsic circadian pacemaker is not entrained to a 24-hour period or is free running with a non-24-hour period (usually slightly longer). The sleep pattern can be quite variable. Some individuals adopt a sleep pattern that is congruent with their free-running pacemaker and shift their sleep times each day in concert with their circadian rhythms.

CIRCADIAN RHYTHM SLEEP DISORDER, JET LAG TYPE (Jet Lag Disorder)

Circadian rhythm sleep disorder, jet lag type, is a circadian rhythm sleep disorder in which there is a temporary mismatch between the timing of the sleep and wake cycle generated by the endogenous circadian clock and that of the sleep and wake pattern required by a change in time zone. Individuals complain of disturbed sleep, decreased subjective alertness, and impaired daytime function. The severity of symptoms is dependent on the number of time zones traveled and the direction of the travel. Eastward travel (requiring advancing circadian rhythms and sleep-wake hours) is usually more difficult to adjust to than westward travel.

CIRCADIAN RHYTHM SLEEP DISORDER, SHIFT WORK TYPE (Shift Work Disorder)

Circadian rhythm sleep disorder, shift work type, is characterized by complaints of insomnia or excessive sleepiness that occur in relation to work hours that are scheduled during the usual sleep period. There are several types of shift-work schedules, including night shifts, early morning shifts, and rotating shifts. The sleep disturbance is most commonly reported in association with the night and early morning shifts. Total sleep time is typically curtailed by one to four hours in night and early morning shift workers, and sleep quality is perceived as unsatisfactory. In addition to impairment of performance at work, reduced alertness may also be associated with consequences for safety. The sleep disorder occurs despite attempts to optimize environmental conditions for sleep. The condition usually persists for the duration of the work-shift period. However, in some individuals, the sleep disturbance may persist beyond the duration of shift work.

CIRCADIAN RHYTHM SLEEP DISORDER DUE TO MEDICAL CONDITION

The etiology of the circadian rhythm sleep disorder is an underlying primary medical or neurological condition. Depending on the underlying neurological or medical disorder, patients may present with a variety of symptoms, including insomnia and excessive sleepiness. The sleep-wake pattern may range from alterations in phase to irregular sleep-wake patterns.

OTHER CIRCADIAN RHYTHM SLEEP DISORDER (Circadian Rhythm Disorder, NOS)

Disorders that: 1) satisfy the criteria of a circadian rhythm sleep disorder, as defined above; 2) are not due to drug or substance; and 3) do not meet criteria for other circadian rhythm sleep disorders are classified here

OTHER CIRCADIAN RHYTHM SLEEP DISORDER DUE TO DRUG OR SUBSTANCE

Disorders that: 1) satisfy the general criteria of a circadian rhythm sleep disorder, as defined above; 2) are due to a drug or substance; and 3) do not meet criteria for other circadian rhythm sleep disorders are classified here.

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Source: American Academy of Sleep Medicine, International Classification of Sleep Disorders, 2nd ed.: Diagnostic and Coding Manual, Westchester, Illinois: American Academy of Sleep Medicine, 2005.