Cyclic alternating pattern (CAP): The marker of sleep instability

Liborio Parrino, Raffaele Ferri, Oliviero Bruni, Mario G. Terzano

Research output: Contribution to journalArticlepeer-review


Cyclic alternating pattern CAP is the EEG marker of unstable sleep, a concept which is poorly appreciated among the metrics of sleep physiology. Besides, duration, depth and continuity, sleep restorative properties depend on the capacity of the brain to create periods of sustained stable sleep. This issue is not confined only to the EEG activities but reverberates upon the ongoing autonomic activity and behavioral functions, which are mutually entrained in a synchronized oscillation. CAP can be identified both in adult and children sleep and therefore represents a sensitive tool for the investigation of sleep disorders across the lifespan. The present review illustrates the story of CAP in the last 25 years, the standardized scoring criteria, the basic physiological properties and how the dimension of sleep instability has provided new insight into pathophysiolology and management of sleep disorders.

Original languageEnglish
Pages (from-to)27-45
Number of pages19
JournalSleep Medicine Reviews
Issue number1
Publication statusPublished - Feb 2012


  • Arousals
  • Cyclic alternating pattern
  • Polysomnography
  • Sleep
  • Sleep disorders

ASJC Scopus subject areas

  • Clinical Neurology
  • Physiology (medical)
  • Pulmonary and Respiratory Medicine
  • Neurology


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