What Are Circadian Rhythm Sleep Disorders?

Circadian rhythm sleep disorders, also referred to as advanced sleep-wake phase disorder (ASWPD)—advanced sleep phase type, advanced sleep phase disorder, advanced sleep phase syndrome—involve a timing problem of when a person sleeps and is awake.

Circadian rhythms are the physical and mental changes that occur throughout the course of your day that affect whether you feel awake or sleepy. These rhythms are regulated by chemicals released in your brain in response to a stimulus, such as light. For example, you wake up in the morning because of chemicals released as your brain reacts to sunlight. Untreated individuals who try to follow conventional bedtimes may develop excessive daytime sleepiness due to a biological inability to sleep later in the morning.

Individuals with ASWPD have a biological clock that is earlier than the general population, so they naturally go to bed and wake up earlier. This disorder can run in families, and there are several genetic mutations that have been associated with this condition.

Delayed sleep phase syndrome (DSPS) is the most common type of circadian sleep disorder. People with DSPS have a tendency to stay up late at night and wake up late in the day. Delayed sleep phase syndrome can interfere with work and school because the sufferer is unable to fall asleep at regular "normal" sleep times.

Other types of circadian sleep disorders include:

  • Delayed sleep phase disorder (DSP)
  • Advanced sleep phase disorder (ASP)
  • Jet lag disorder
  • Shift work disorder
  • Irregular sleep-wake rhythm
  • Free-running (nonentrained) type