Sleep Disorders: Circadian Rhythm Disorders
Circadian rhythm disorders are disruptions in a persons circadian rhythm -- a
name given to the "internal body clock" that regulates the (approximately)
24-hour cycle of biological processes in animals and plants. 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 "clock" in humans is located mainly in the suprachiasmatic
nucleus (SCN), which is a group of cells located in the hypothalamus (a portion
of the brain). Circadian rhythms are important in determining human sleeping
What Causes Circadian Rhythm Disorders?
Circadian rhythm disorders can be
caused by many factors, including:
- Shift work
- Time zone changes
- Changes in routine
Circadian Rhythm Disorders
- Jet Lag or Rapid Time Zone Change Syndrome: This syndrome consists of symptoms including
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 at very late times and have difficulty waking up in time for work,
school, or social engagements.
Sleep Phase Syndrome: Advanced sleep phase syndrome is a disorder in which the major
sleep episode is advanced in relation to the desired clock time. This syndrome
results in symptoms of evening sleepiness, an early sleep onset, and waking up
earlier than desired.
- Non 24-Hour Sleep Wake Disorder: Non 24-hour
sleep wake disorder is a condition in which an individual has a normal sleep
pattern but lives in a 25-hour day. Throughout time the persons 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.