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Sleep and Circadian Rhythm Disorders

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Circadian rhythm disorders are disruptions in a person's circadian rhythm -- a name given to the "internal body clock" that regulates the (approximately) 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.

The circadian rhythm is important in determining sleeping patterns such as when we sleep and when we wake, every 24 hours.The normal circadian clock is set by the light-dark cycle over 24 hours.

Recommended Related to Sleep Disorders

Insomnia Got You Up (Again)?

Sleep has never been easy for Leslie Partridge Sachs, a dancer, choreographer, and mother of two young girls who lives in Garrison, N.Y. Even as a child, she says, "I had trouble falling asleep and staying asleep." Once she became a mother, her insomnia worsened. "I sleep very lightly -- I hear my daughters even if they turn over in bed. And most mornings I wake up at 3:30 or 4 and can’t get back to sleep." Her average night’s shut-eye of four to five hours affects her mood. "I feel irritable,"...

Read the Insomnia Got You Up (Again)? article > >


What Causes Circadian Rhythm Disorders?

Circadian rhythm disorders can be caused by many factors, including:


Common Circadian Rhythm Disorders

  • Jet Lag or Rapid Time Zone Change Syndrome: This syndrome consists of symptoms that include excessive sleepiness and a lack of daytime alertness in people who travel across time zones.
  • Shift Work Sleep Disorder: This sleep disorder affects people who frequently rotate shifts or work at night.
  • Delayed Sleep Phase Syndrome (DSPS): This is a disorder of sleep timing. People with DSPS tend to fall asleep very late at night and have difficulty waking up in time for work, school, or social engagements.
  • Advanced Sleep Phase Syndrome (ASPD): This is a disorder in which a person goes to sleep earlier and wakes earlier than desired. ASPD results in symptoms of evening sleepiness, going to bed earlier (for example, between 6 p.m. and 9 p.m.), and waking up earlier than desired (for example, between 1 a.m. and 5 a.m.)
  • Non 24-Hour Sleep Wake Disorder: This disorder frequently affects those that are totally blind since the circadian clock is set by light-dark cycle over a 24 hour period. In non-24 hour sleep wake disorder the cycle is disturbed. The disorder result in drastically reduced sleep time and sleep quality at night and problems with sleepiness during daylight hours.


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