The essential feature of Circadian Rhythm Sleep Disorder is a persistent or recurrent pattern of sleep disruption that results from altered function of the circadian timing system or from a mismatch between the individual’s endogenous circadian sleep-wake system and exogenous demands regarding the timing and duration of sleep (Criterion A). In contrast to other primary Sleep Disorders, Circadian Rhythm Sleep Disorder does not result from dysfunction of the mechanisms generating sleep and wakefulness per se. As a result of the circadian mismatch, individuals with this disorder may complain of insomnia at certain times during the 24-hour day and excessive sleepiness at other times, with resulting impairment in social, occupational, or other important areas of functioning or marked subjective distress (Criterion B). The sleep problems are not better accounted for by other Sleep Disorders or other mental disorders (Criterion C) and are not due to the direct physiological effects of a substance or a general medical condition (Criterion D).
The diagnosis of Circadian Rhythm Sleep Disorder should be reserved for those presentations in which the individual has significant social or occupational impairment or marked distress related to the sleep disturbance. Individuals vary widely in their ability to adapt to circadian changes and requirements. Many, if not most, individuals with circadian-related symptoms of sleep disturbance do not seek treatment and do not have symptoms of sufficient severity to warrant a diagnosis. Those who present for evaluation because of this disorder are most often troubled by the severity or persistence of their symptoms. For example, it is not unusual for shift workers to present for evaluation after falling asleep while on the job or while driving.
The diagnosis of Circadian Rhythm Sleep Disorder rests primarily on the clinical history, including the pattern of work, sleep, naps, and “free time.” The history should also examine past attempts at coping with symptoms, such as attempts at advancing the sleep-wake schedule in Delayed Sleep Phase Type. Prospective sleep-wake diaries or sleep charts are often a useful adjunct to diagnosis.
Delayed Sleep Phase Type. This type of Circadian Rhythm Sleep Disorder is characterized by a delay of circadian rhythms, including the sleep-wake cycle, relative to the demands of society. Measurement of endogenous circadian rhythms (e.g., core body temperature, plasma melatonin levels) during the individual’s usual (i.e., delayed) sleep-wake schedule reflects this delay. Individuals with this subtype are hypothesized to have an abnormally diminished ability to phase-advance sleep-wake hours (i.e., to move sleep and wakefulness to earlier clock times) or an alteration in the usual alignment of sleep with other circadian rhythms. As a result, these individuals are “locked in” to habitually late sleep hours and have great difficulty shifting these sleep hours forward to an earlier time. The circadian phase of sleep is stable: individuals will fall asleep and awaken at consistent, albeit delayed, times when left to their own schedule (e.g., on weekends or vacations). Affected individuals complain of difficulty falling asleep at socially acceptable hours, but once sleep is initiated, it is normal. There is concomitant difficulty awakening at socially acceptable hours (e.g., multiple alarm clocks are often unable to arouse the individual). Many individuals with this disorder will be chronically sleep deprived as a result of the need to awaken for social and occupational obligations in the morning. Sleepiness during the desired wake period may result.
Jet Lag Type. In this type of Circadian Rhythm Sleep Disorder, the endogenous circadian sleep-wake cycle is normal and the disturbance arises from conflict between the pattern of sleep and wakefulness generated by the circadian system and the pattern of sleep and wakefulness required by a new time zone. Individuals with this type complain of a mismatch between desired and required hours of sleep and wakefulness. The severity of symptoms is proportional to the number of time zones traveled, with maximal difficulties often noted after traveling through eight or more time zones in less than 24 hours. Eastward travel (advancing sleep-wake hours) is typically more difficult for most individuals to tolerate than westward travel (delaying sleep-wake hours).
Shift Work Type. In this type of Circadian Rhythm Sleep Disorder, the endogenous circadian sleep-wake cycle is normal and the disturbance arises from conflict between the pattern of sleep and wakefulness generated by the circadian system and the desired pattern of sleep and wakefulness required by shift work. Night-shift schedules (with shifting back to a day schedule on days off) and rotating-shift schedules are the most disruptive because they force sleep and wakefulness into aberrant circadian positions and prevent any consistent adjustment. Workers on these shifts typically have a shorter sleep duration and more frequent disturbances in sleep continuity than morning and afternoon workers. Conversely, these individuals may feel sleepy or fall asleep during the desired wake period, that is, in the middle of the night work shift. Work schedules that involve slowly rotating shifts or rotations to progressively earlier shifts (i.e., nights-afternoons-days) are also associated with higher degrees of sleep disturbance and other complaints than other types of rotating-shift schedules. The circadian mismatch of the Shift Work Type is further exacerbated by insufficient sleep time, social and family demands, alcohol use, and environmental disturbances (e.g., telephone, traffic noise) during intended sleep times.
Unspecified Type. This type of Circadian Rhythm Sleep Disorder should be indicated if another pattern of circadian sleep disturbance (e.g., advanced sleep phase, non-24-hour sleep-wake pattern, or irregular sleep-wake pattern) is present. An “advanced sleep phase pattern” is the analog of Delayed Sleep Phase Type, but in the opposite direction: individuals complain of an inability to stay awake in the evening and spontaneous awakening in the early morning hours. “Non-24-hour sleep-wake pattern” denotes a free-running cycle: the sleep-wake schedule follows the endogenous circadian rhythm period of slightly over 24 hours despite the presence of 24-hour time cues in the environment. In contrast to the stable sleep-wake pattern of the Delayed or advanced sleep phase types, these individuals’ sleep-wake schedules become progressively delayed relative to the 24-hour clock, resulting in a changing sleep-wake pattern and changing sleep-wake complaints over successive days (e.g., several days of sleep-onset insomnia followed by days of daytime sleepiness followed by days of difficulty staying awake in the evening). “Irregular sleep-wake pattern” indicates the absence of an identifiable pattern of sleep and wakefulness.
Associated Features and Disorders
Associated descriptive features and mental disorders. In Delayed Sleep Phase Type, individuals frequently go to bed later and wake up later on weekends or during vacations, with a reduction in sleep-onset difficulties and difficulty awakening. They will typically give many examples of school, work, and social difficulties arising from their difficulty awakening at socially desired times. If awakened earlier than the time dictated by the circadian timekeeping system, the individual may demonstrate “sleep drunkenness” (i.e., extreme difficulty awakening, confusion, and inappropriate behavior). Performance often also follows a delayed phase, with peak efficiency occurring in late-evening hours.
Jet Lag Type may be more common in individuals who are “morning larks.” It is often accompanied by other symptoms such as impaired concentration and memory, impaired coordination, weakness, lightheadedness, headache, fatigue, malaise, decreased appetite, and indigestion. These symptoms may relate not only to circadian mismatch but also to other travel conditions such as sleep deprivation, alcohol and caffeine use, and decreased ambient air pressure in airplanes. Performance is often impaired, following the pattern that would be predicted by the underlying endogenous circadian rhythms. Shift Work Type may also be more common in individuals who are “morning types.” Concentration and attention, performance, and alertness are often impaired during desired waking hours, following the pattern that would be predicted by the underlying endogenous circadian rhythms. Reduced quality of life and dysfunction in occupational, family, and social roles are often observed in shift workers, particularly those who have sleep difficulties. Shift work is a risk factor for sleepiness-related work and motor vehicle accidents.
The non-24-hour sleep-wake pattern has been described primarily in blind individuals, particularly those with no light perception (e.g., from retrolental fibroplasia or surgical enucleation) as opposed to those with some degree of conscious light perception. Napping and regularly recurring insomnia occur when the individual’s endogenous circadian rhythms (which are slightly longer than 24 hours) are out of phase with the light-dark cycle and socially appropriate sleep-wake hours.
Individuals with any Circadian Rhythm Sleep Disorder may use increased amounts of alcohol, sedative-hypnotic, or stimulants in an attempt to control their inappropriately phased sleep-wake tendencies. The use of these substances may in turn exacerbate the Circadian Rhythm Sleep Disorder. Delayed Sleep Phase Type has been associated with schizoid, schizotypal, and avoidant personality features, particularly in adolescents, as well as with depressive symptoms and Depressive Disorders. “Non-24-hour sleep-wake pattern” and “irregular sleep-wake pattern” have also been associated with these same features. Jet Lag and Shift Work Types may precipitate or exacerbate a Manic or Major Depressive Episode or an episode of a Psychotic Disorder. Shift work is also associated with depressive symptoms.
Associated laboratory findings. Sleep studies yield different results depending on what time they are performed. For individuals with Delayed Sleep Phase Type, studies conducted at the preferred sleep times will be essentially normal for age. However, when studied at socially normal sleep times, these individuals have prolonged sleep latency, reduced sleep efficiency (due mainly to sleep-onset difficulties), short sleep duration, and, in some individuals, moderately short REM sleep latency. Laboratory procedures designed to measure the phase of the endogenous circadian pacemaker (e.g., core body temperature, plasma melatonin levels) reveal the expected phase delay in the timing of acrophase (peak time) and nadir when individuals are studied during their usual sleep-wake times. In addition, awakening time may be delayed relative to other circadian rhythms.
When studied during their habitual workweek sleep hours, individuals with Shift Work Type usually have normal or short sleep latency, reduced sleep duration, and more frequent sleep continuity disturbances compared with age-matched individuals with “normal” nocturnal sleep patterns. There may be a specific reduction in stage 2, stages 3 and 4, and REM sleep in many cases. Polysomnographic patterns in shift workers have been shown to remain stable over intervals of 2 years, suggesting neither adaptation nor worsening. Measures of physiological sleepiness, such as the Multiple Sleep Latency Test (MSLT), show a high degree of sleepiness during desired wake times (e.g., during the night shift). After a period of adjustment to a normal diurnal schedule, these individuals have normal nocturnal sleep and normal levels of daytime sleepiness. When studied on their usual shift-work schedules in their usual environment, shift workers demonstrate changes in the overt timing of their circadian rhythms relative to normal diurnal patterns. However, these changes seldom if ever result in a complete nocturnal orientation. Interventions such as bright light can shift endogenous circadian rhythms into phase with the night shift, but this does not necessarily improve subjective complaints or performance. Night shift work may be associated with increases in triglyceride or cholesterol levels.
Laboratory studies of simulated jet lag demonstrate prolonged sleep latency, impaired sleep efficiency, reductions in REM sleep, and minor reductions in slow-wave sleep. These features recover toward baseline values over 1-2 weeks and are more severe with simulated eastward travel (i.e., advanced sleep hours) than with simulated westward travel (i.e., delayed sleep hours). Other laboratory measures, including circadian rhythms of melatonin, core body temperature, alertness, and performance, also take several days or weeks to adjust following simulated jet lag. Non-24-hour sleep-wake pattern in blind individuals is often characterized by “free-running” circadian rhythms of core body temperature, melatonin secretion, and sleep propensity. In other words, these rhythms have a period of slightly longer than 24 hours, similar to those of sighted individuals deprived of all time cues in experimental settings. Individuals with “advanced sleep phase pattern,” as expected, show earlier timing of endogenous circadian rhythms, as well as a shortening of the endogenous circadian rhythm period.
Associated physical examination findings and general medical conditions. No specific physical findings are described for Circadian Rhythm Sleep Disorder. Shift workers may appear haggard or sleepy and may have an excess of gastrointestinal disturbances, including gastritis and peptic ulcer disease. The roles of caffeine and alcohol consumption and altered eating patterns have not been fully evaluated in these cases. Shift work has been associated with risk factors for cardiovascular disease, such as hypertension, “nondipping” 24-hour blood pressure patterns, increased atherogenic lipids, and abnormal electrocardiographic measures (prolonged QTc interval). It may also be associated with a slightly increased risk for actual cardiovascular disease, although not all studies have found this. Non-24-hour sleep-wake pattern often occurs in blind individuals, particularly those with no light perception. Circadian Rhythm Sleep Disorder may exacerbate preexisting general medical conditions.
Specific Age Features
The onset of Delayed Sleep Phase Type most often occurs between late childhood and early adulthood. Shift work and jet lag symptoms are often reported to be more severe, or more easily induced in laboratory settings, in late-middle-aged and elderly individuals compared with young adults. Older adults also have more severe polysomnographic sleep disturbances following simulated jet lag in the laboratory, but their circadian rhythms appear to adjust at the same rate as younger adults. “Advanced sleep phase pattern” also increases with age. These findings may result from age-related deterioration in nocturnal sleep and shortening of the endogenous circadian period.
The prevalence for any of the types of Circadian Rhythm Sleep Disorder has not been well established. Prevalence figures for the Delayed Sleep Phase Type from population surveys have varied widely, ranging from 0.1% to 4% in adults and up to 7% in adolescents. Up to 60% of night shift workers may have Shift Work Type.
Delayed Sleep Phase Type typically begins during adolescence and may follow a psychosocial stressor. Without intervention, Delayed Sleep Phase Type typically lasts for years or decades but may “correct” itself given the tendency for endogenous circadian rhythm phase to advance with age. Treatment can often normalize sleep hours at least temporarily, but there is a persistent vulnerability for delayed sleep hours and other symptoms.
Shift Work Type typically persists for as long as the individual works that particular schedule. Reversal of symptoms generally occurs within 2 weeks of a return to a normal diurnal sleep-wake schedule.
Experimental and field data concerning jet lag indicate that it takes approximately 1 day per time zone traveled for the circadian system to resynchronize itself to the new local time. Different circadian rhythms (such as core body temperature, hormonal level, alertness, and sleep patterns) may readjust at different rates.
A family history may be present in up to 40% of individuals with Delayed Sleep Phase Type. A familial form of Advanced Sleep Phase Type, segregating as an autosomal dominant trait with high penetrance, has been identified.
Circadian Rhythm Sleep Disorder must be distinguished from normal patterns of sleep and normal adjustments following a change in schedule. The key to such distinctions lies in the persistence of the disturbance and the presence and degree of social or occupational impairment. For instance, many adolescents and young adults maintain delayed sleep-wake schedules, but without distress or interference with school or work routines. Likewise, many individuals characterize themselves as either “night owls” or “morning larks,” because of their preference for either late or early sleep schedules. These tendencies in themselves do not warrant a diagnosis of Delayed Sleep Phase Type or “advanced sleep phase pattern.” A diagnosis would be made only in individuals who persistently experience clinically significant distress or impairment and who have difficulty changing their sleep-wake pattern. Similarly, almost anyone who travels across time zones will experience transient sleep disruption. The diagnosis of the Jet Lag Type should be reserved for individuals with associated severe sleep disturbances and work disruption.
Delayed Sleep Phase Type must be differentiated from volitional patterns of delayed sleep hours. Some individuals who voluntarily delay sleep onset to participate in social or work activities may complain of difficulty awakening. When permitted to do so, these individuals fall asleep readily at earlier times and, after a period of recovery sleep, have no significant difficulty awakening in the morning. In such cases, the primary problem is sleep deprivation rather than a Circadian Rhythm Sleep Disorder. Other individuals (particularly children and adolescents) may volitionally shift sleep hours to avoid school or family demands. The pattern of difficulty awakening vanishes when desired activities are scheduled in the morning hours. In a similar way, younger children involved in limit-setting battles with parents may present as having Delayed Sleep Phase Type.
Jet Lag and Shift Work Types must be distinguished mainly from other primary Sleep Disorders, such as Primary Insomnia and Primary Hypersomnia. The history of jet lag or shift work, with undisturbed sleep on other schedules, usually provides sufficient evidence to exclude these other disorders. In some cases, other primary Sleep Disorders, such as Breathing-Related Sleep Disorder or periodic limb movements disorder, may complicate Shift Work or Jet Lag Types. This possibility should be suspected when reversion to a normal diurnal schedule does not provide relief from sleep-related symptoms. Other types of Circadian Rhythm Sleep Disorder, such as “non-24-hour sleep-wake pattern” and “irregular sleep-wake pattern,” are distinguished from the Delayed Sleep Phase Type by the stable pattern of delayed sleep-wake hours characteristic of the latter.
Patterns of delayed or advanced sleep that occur exclusively during another mental disorder are not diagnosed separately. For instance, an individual with Major Depressive Disorder may have delayed sleep hours similar to those in Delayed Sleep Phase Type, but if this sleep pattern occurs only during the Major Depressive Episode, an additional diagnosis of Circadian Rhythm Sleep Disorder would not be warranted. Likewise, an individual experiencing an acute exacerbation of Schizophrenia may have a very irregular sleep-wake pattern, but if this sleep pattern is only associated with the exacerbation, no additional diagnosis of Circadian Rhythm Sleep Disorder would be made.
Substances (including medications) can cause delayed sleep onset or awakening in the morning. For instance, consumption of caffeine or nicotine in the evening may delay sleep onset, and the use of hypnotic medications in the middle of the night may delay the time of awakening. A diagnosis of Substance-Induced Sleep Disorder may be considered if the sleep disturbance is judged to be a direct physiological consequence of regular substance use and warrants independent clinical attention. General medical conditions rarely cause fixed delays or advances of the sleep-wake schedule and typically pose no difficulty in differential diagnosis.
Relationship to the International Classification of Sleep Disorders
The International Classification of Sleep Disorders (ICSD) includes categories for Delayed Sleep Phase Syndrome, Shift Work Sleep Disorder and Time Zone Change (Jet Lag) Syndrome, and specific categories for three other Circadian Rhythm Sleep Disorders (Irregular Sleep-Wake Pattern, Advanced Sleep Phase Syndrome, and Non-24-Hour Sleep-Wake Syndrome).
Diagnostic criteria for 307.45 Circadian Rhythm Sleep Disorder
A. A persistent or recurrent pattern of sleep disruption leading to excessive sleepiness or insomnia that is due to a mismatch between the sleep-wake schedule required by a person’s environment and his or her circadian sleep-wake pattern.
B. The sleep disturbance causes clinically significant distress or impairment in social, occupational, or other important areas of functioning.
C. The disturbance does not occur exclusively during the course of another Sleep Disorder or other mental disorder.
D. The disturbance is not due to the direct physiological effects of a substance (e.g., a drug of abuse, a medication) or a general medical condition.
Delayed Sleep Phase Type: a persistent pattern of late sleep onset and late awakening times, with an inability to fall asleep and awaken at a desired earlier time
Jet Lag Type: sleepiness and alertness that occur at an inappropriate time of day relative to local time, occurring after repeated travel across more than one time zone
Shift Work Type: insomnia during the major sleep period or excessive sleepiness during the major awake period associated with night shift work or frequently changing shift work
Revision date: June 20, 2011
Last revised: by Tatiana Kuznetsova, D.M.D.