A circadian rhythm sleep disorder is a persistent pattern of sleep disruption that is primarily due to a misalignment between the body’s circadian rhythm (biological clock) and the sleep-wake schedule required by an individual’s physical environment or social or professional schedule. A diagnosis of a circadian rhythm sleep disorder is based on:

• The sleep disruption leading to excessive sleepiness and/or insomnia.
• The sleep disturbance causing significant distress or impairment in social, occupational, and other important areas of functioning.

There are several different types of circadian rhythm sleep disorders. They include:

• Delayed Sleep Phase Type
  This type of sleep disorder occurs when a person’s biological clock runs slower than 24 hours or is shifted later than the desired schedule. This produces a phase delay in the sleepiness-alertness cycle. Individuals with delayed sleep phase are more alert in the evening and early nighttime, stay up later, and are more tired in the morning. These individuals are commonly referred to as “night owls.”
  
• Irregular Sleep-Wake Type
  The irregular sleep-wake pattern occurs when the circadian sleep-wake rhythm is absent or diminished. Individuals with this condition have a normal amount of sleep during a 24-hour period; however, it is fragmented into three or more sleep episodes that occur irregularly. Long daytime naps and nocturnal wakefulness occur with symptoms of insomnia at night and excessive sleepiness during the day. A history of reclusion or isolation may be associated with this condition. This type of sleep disorder is typically associated with neurodegenerative disorders, such as Alzheimer’s disease and some neurodevelopmental issues in children.
  
• Shift Work Type
  This irregular sleep-wake pattern occurs with individuals who work the night shift but retain an unshifted circadian rhythm. Furthermore, to meet social demands, shift workers often adopt a non-shifted sleep-wake schedule on weekends and holidays. The result can be severe insomnia when attempting to sleep and excessive sleepiness when trying to stay awake.
  
• Jet Lag Type
  This irregular sleep-wake pattern can occur when an individual rapidly travels across many time zones. Those who frequently travel for business can find themselves quite impaired at the time they need to make important decisions. “Night owls” will experience greater difficulty adjusting to eastward travel, while “larks” will have more problems with westward travel. Normally, healthy individuals can easily adapt to one to two time zone changes per day. Natural adjustment to an 8-hour translocation may take 4 or more days.
  
• Due to Medical Condition
  Patients who are bedridden, hospitalized, or dealing with some forms of dementia, often sleep ad lib. The resulting chaotic sleep-wake pattern adversely affects the circadian rhythm, which may be further exacerbated by medication with sedative properties.

What are treatments for Circadian Rhythm Sleep Disorders?

There are several approaches for treating circadian rhythm sleep disorders. These include the following:

• Chronotherapy
  Chronotherapy is one technique used to reset the biological clock. It involves progressively phase-delaying a person’s sleep time until their biological clock is synchronized with the desired sleep-wake schedule. 
  
• Light or Phototherapy
  Studies indicate that exposing an individual to bright lights (greater than 10,000 lux) can alter their biological rhythm. With precise timing of bright light exposure, the biological clock can be stopped and reset. The blue part of the light spectrum is the crucial ingredient in phase setting and shifting. Light therapy is used to reset the circadian rhythm of shift workers, astronauts, and individuals experiencing jet lag.
  
• Melatonin
  Melatonin supplements have been proven effective in treating circadian rhythm disorders in blind patients. Under normal circumstances, melatonin levels begin to rise at dusk and remain elevated until dawn. Bright light suppresses the release of melatonin. Ramelteon, a synthetic melatonin agonist, is FDA-approved for treating patients with sleep-onset insomnia but is used off label for the entire spectrum of circadian rhythm sleep disorders.

• Modafinil
  Modafinil is a wake-promoting drug used to treat excessive daytime sleepiness due to narcolepsy, obstructive sleep apnea, and shift work disorder.