Circadian Rhythm Sleep Wake Disorders

Body Rhythms & Abnormal behaviours during sleep can take many forms

Circadian rhythm sleep wake disorders are characterized by a disturbance or disruption to the normal circadian rhythm which causes the patient to experience excessive daytime sleepiness, insomnia, or both.
The human body has a master circadian clock in a control center of the brain known as suprachiasmatic nucleus (SCN).
This internal clock regulates the timing of body rhythms such as temperature and hormone levels.
The master circadian body clock controls the sleep-wake cycle.
The circadian clock is set primarily by visual cues of light and darkness that are communicated along a pathway from the eyes to the SCN. This keeps the clock synchronized to the 24-hour day.
Other time cues, known as Zeitgebers, also can influence the clocks timing. These include meal and exercise schedules.

Each circadian rhythm sleep disorder involves one of these two problems:

Delayed sleep -wake disorder is characterized by a later sleep time than expected or desired.
A patient with this disorder is unable to fall asleep at the desired time or at a time that is considered normal but is able to at a later time in the night.
The patient then sleeps until late in the morning.
This disorder is common in adolescents or young adults who develop habits of staying up late at night.

Advanced sleep-wake phase disorder is characterized by an earlier sleep time than expected or desired.
A patient with this disorder has difficulty staying awake until the normal or expected bedtime, but then awakens early in the morning.
This is common in older adults who develop the lifestyle of eating and sleeping at earlier times then they did at younger ages.

Irregular sleep-wake rhythm disorder is characterized by abnormal sleep and wake time.
Although the total sleep time during the 24-hour cycle is comparable with normal sleepers, the sleep period may come in the form of several naps as opposed to one main sleep period.
The patient also experiences periods of insomnia and EDS.

Formerly called free- running disorder, non 24 hour sleep-wake rhythm sleep disorder is characterized by a circadian rhythm not consistent with the 24 hour clock.
The patient circadian rhythm is often longer than 24 hour and does not seem to be related to the light-dark cycle.
Many patients with this disorder are blind.

Patient with shift work disorder are assigned to work a shift that occurs during the late night or early morning hours, such as the graveyard shift.
As a result many of the disturbances of the circadian rhythm, the patient typically experiences EDS.
As a result, many of these workers have poor work performance, impaired judgment and reduced wakefulness while at work.
Much research has been done on the topic of shift work and it’s effect on the human body as more and more people are assigned to work during the normal sleep period.

Jet lag disorder occurs when a person travels across two or more time zones, resulting in EDS or insomnia.
Other symptoms such as gastrointestinal disturbances or poor performance often occur.