Specify whether: 307.45 (647.21) Delayed sleep phase type: A pattern of delayed sleep onset and awakening times, with an inability to fall asleep and awaken at a desired or convention- ally acceptable earlier time.
Specify if:
Familial: A family history of delayed sleep phase is present.
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Overlapping with non-24-hour sleep-wake type: Delayed sleep phase type may overlap with another circadian rhythm sleep-wake disorder, non-24-hour sleep-wake type.
307.45 (647.22) Advanced sleep phase type: A pattern of advanced sleep onset and awakening times, with an inability to remain awake or asleep until the desired or con- ventionally acceptable later sleep or wake times.
Specify if:
Familial: A family history of advanced sleep phase is present.
307.45 (647.23) Irregular sleep—wake type: A temporally disorganized sleep-wake pattern, such that the timing of sleep and wake periods is variable throughout the 24- hour period.
307.45 (647.24) Non-24-hour sleep—wake type: A pattern of sleep-wake cycles that is not synchronized to the 24-hour environment, with a consistent daily drift (usually to later and later times) of sleep onset and wake times.
307.45 (647.26) Shift work type: Insomnia during the major sleep period and/or ex- cessive sleepiness (including inadvertent sleep) during the major awake period asso- ciated with a shift work schedule (i.e., requiring unconventional work hours).
307.45 (647.20) Unspecified type
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Episodic: Symptoms last at least 1 month but less than 3 months.
Persistent: Symptoms last 3 months or longer.
Recurrent: Two or more episodes occur within the space of 1 year.
The delayed sleep phase type is based primarily on a history of a delay in the timing of the major sleep period (usually more than 2 hours) in relation to the desired sleep and wake— up time, resulting in symptoms of insomnia and excessive sleepiness. When allowed to set their own schedule, individuals with delayed sleep phase type exhibit normal sleep qual- ity and duration for age. Symptoms of sleep—onset insomnia, difficulty waking in the morning, and excessive early day sleepiness are prominent.
Common associated features of delayed sleep phase type include a history of mental dis- orders or a concurrent mental disorder. Extreme and prolonged difficulty awakening with morning confusion is also common. Psychophysiological insomnia may develop as a re- sult of maladaptive behaviors that impair sleep and increase arousal because of repeated attempts to fall asleep at an earlier time.
Prevalence of delayed sleep phase type in the general population is approximately 0.17% but appears to be greater than 7% in adolescents. Although the prevalence of familial de- layed sleep phase type has not been established, a family history of delayed sleep phase is present in individuals with delayed sleep phase type.
Course is persistent, lasting longer than 3 months, with intermittent exacerbations through- out adulthood. Although age at onset is variable, symptoms begin typically in adolescence and early adulthood and persist for several months to years before diagnosis is estab- lished. Severity may decrease with age. Relapse of symptoms is common.
Clinical expression may vary across the lifespan depending on social, school, and work obligations. Exacerbation is usually triggered by a change in work or school schedule that requires an early rise time. Individuals who can alter their work schedules to accommo- date the delayed circadian sleep and wake timing can experience remission of symptoms.