What are Circadian Rhythm Disorders?

June 8, 2006

From the Cleveland Clinic Health Information Center website:
Circadian rhythm disorders are disruptions in a person’s circadian rhythm, the "internal body clock" that regulates the 24-hour cycle of biological processes. The term circadian comes from Latin words that literally mean "around the day." There are patterns of brain wave activity, hormone production, cell regeneration, and other biological activities linked to this 24-hour cycle. Circadian rhythms determine a person’s sleeping patterns.

What causes circadian rhythm disorders?
Circadian rhythm disorders can be caused by many factors, including:

• Shift work
• Pregnancy
• Time zone changes
• Medicines
• Changes in routine

Common circadian rhythm disorders:

• Jet lag or rapid time zone change syndrome: Sleep disruptions of people who travel across time zones.
• Shift work sleep disorder: Affects people who frequently rotate shifts or work at night
• Delayed sleep phase syndrome (DSPS): People with DSPS tend to fall asleep at very late times and have difficulty waking up in time for normal work, school, or social engagements.
• Advanced sleep phase syndrome: This syndrome results in symptoms of evening sleepiness, an early sleep onset, and waking up earlier than desired.
• Non 24-hour sleep wake disorder: A condition in which an individual has a normal sleep pattern but lives in a 25-hour day. Throughout time the person’s sleep cycle will drift in and out of normal societal norms, sometimes falling asleep at a later time and waking up later, and sometimes falling asleep at an earlier time and waking up earlier.

How are circadian rhythm disorders treated?
Therapy usually combines proper sleep hygiene techniques and external stimulus therapy such as bright light therapy or chronotherapy. Chronotherapy is a behavioral technique in which the bedtime is systematically adjusted. Bright-light therapy is designed to reset a person’s circadian rhythm to a desired pattern. When combined, these therapies might produce significant results in people with circadian rhythm disorders.

Read