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Sleep-Wake Phase Disorders

What are Sleep-Wake Phase Disorders?

Circadian rhythm sleep-wake phase disorders involve abnormalities in the body’s sleep rhythms. The body’s circadian rhythm governs sleep-wake cycles according to biological cues like hormone levels and body temperature, and environmental factors such as light exposure and mealtimes.

Like other circadian rhythm sleep disorders, sleep-wake phase disorders occur when the circadian rhythm does not align with normal sleep patterns. People with sleep-wake phase disorders have a strong biological drive to sleep during times when most others are awake, or wake when most others are asleep. They may complain of early-morning insomnia or call themselves a “night owl.” They may feel tired as early as 6 p.m. or stay up until the wee hours of the morning without feeling an urge to sleep. These disordered sleep patterns make it difficult to perform daily activities, socialize, or hold a job.

Those with sleep-wake phase disorders may experience excessive daytime sleepiness because they have trouble establishing and maintaining consistent sleep patterns.

Symptoms of Sleep-Wake Phase Disorders

  • A sleep period that is delayed or advanced by at least 2 hours
  • Trouble sleeping for long periods at night
  • Difficulty falling asleep at night
  • Difficulty waking in the morning
  • Excessive daytime sleepiness

Types of Sleep-Wake Phase Disorders

Advanced sleep-wake phase disorder (also called advanced sleep-phase syndrome) involves a shift in the circadian rhythm corresponding with early bedtimes and arousals. People with advanced sleep-wake phase disorder experience a strong urge to fall asleep in the evening, generally between 6 p.m. and 9 p.m., and wake too early in the morning, generally between 2 a.m. and 5 a.m. They are tired during the day, making it more likely to fall asleep early the following evening. An estimated 1 percent of adults experience ASPD, which is more common in older adults.

Delayed sleep-wake phase disorder (also called delayed sleep-phase syndrome) occurs when the circadian rhythm shifts and sleep occurs later in the 24-hour cycle. People with delayed sleep-wake phase disorder generally fall asleep 2 or more hours later than their preferred bedtime. They experience extreme difficulty waking in the morning and can experience excessive daytime sleepiness; despite being tired during the day, they are awake at night. Because teenagers experience a natural sleep phase delay during puberty, delayed sleep phase disorder is more common in adolescents and more common in girls than boys.

What Causes Sleep-Wake Phase Disorders?

Sleep-wake phase disorders arise from the circadian rhythm, the master clock controlling biological patterns. Conditions affecting the brain, including injury and neurological conditions like dementia, make sleep-wake phase disorders more likely. Adolescents, elderly patients and blind individuals have a higher risk of sleep-wake phase disorders.

Family history may play a role: Researchers have identified mutations in two genes, hPer2 and CSK1D, linked to an increased risk for sleep-wake phase disorders.


Healthcare providers may use clinical criteria (patient’s own reports of sleep patterns and symptoms) to diagnose sleep-wake phase disorders. Patients may be asked to keep a sleep diary to record sleep patterns for several weeks. Actigraphy can help track sleep and wake patterns to aid clinicians in diagnosing sleep-wake phase disorders.


Treating sleep-wake phase disorders depends on their severity and impact on the patient’s day-to-day life. Because some adolescents naturally outgrow their sleep phase delay as they mature, treatment is not necessary. Some people with sleep-wake phase disorders can adjust their daily lives to correspond with their advanced or delayed sleep patterns.

However, some people experience significant difficulties in their personal and professional lives as a result of sleep-wake phase disorders. For people who want to correct their phase disorder, light therapy and supplemental melatonin, administered at specific times, have been proven effective for adults, children, and elderly patients with sleep-wake phase disorder; some researchers recommend against the use of melatonin therapy for elderly patients with dementia.

For example, for someone with advanced sleep-wake phase disorder, bright light therapy between 7 p.m. and 9 p.m. can help shift the circadian rhythm later to align with a more desirable sleep schedule. For someone with delayed sleep-phase disorder, bright light therapy in the morning can promote wakefulness during the day and an easier transition into sleep at bedtime.

Additional resources
Excessive daytime sleepiness
Circadian rhythms, explained

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