Irregular Sleep Phase Type

Prevalence

Prevalence of irregular sleep-wake type in the general population is unknown.

Risk Factors

Environmental

  • Decreased exposure to environmental light and structured daytime activity can be associated with a low-amplitude circadian rhythm.

  • Hospitalized individuals are especially prone to such weak external entraining stimuli, and even outside the hospital setting, individuals with major neurocognitive disorder (i.e., dementia) are exposed to significantly less bright light.


Temperamental

Neurodegenerative disorders, such as Alzheimer's disease, Parkinson's disease, and Huntington's disease, and neurodevelopmental disorders in children increase the risk for irregular sleep-wake type.

Diagnostic Features

  • The diagnosis of irregular sleep-wake type is based primarily on a history of symptoms of insomnia at night (during the usual sleep period) and excessive sleepiness (napping) during the day.

  • Irregular sleep-wake type is characterized by a lack of discernable sleep-wake circadian rhythm.

  • There is no major sleep period, and sleep is fragmented into at least three periods during the 24-hour day.