Circadian Rhythm Sleep-Wake Disorders
Circadian rhythm sleep-wake disorders are a group of conditions in which the timing of an individual’s sleep is disrupted. Circadian rhythms are often referred to as the body’s internal clock or our “biological clock.” People with a circadian rhythm sleep-wake disorder may be unable to naturally go to sleep or wake up at the time necessary for their work, school, or social environments.
The specific types of circadian rhythm sleep-wake disorders, as listed in the Diagnostic and Statistical Manual of Mental Disorders (DSM), include the delayed sleep phase type, the advanced sleep phase type, the irregular sleep-wake type, the non-24-hour sleep-wake type, and the shift-work type.
A diagnosis of a circadian rhythm sleep-wake disorder is only given if a person’s sleep disturbance causes clinically significant distress or impairs their ability to function in social, occupational, or educational settings.
- The delayed sleep phase type is a sleep pattern in which a person falls asleep two or more hours after they intend to. As a result, they have difficulty waking in the morning and are excessively sleepy during the first part of the day. When people with this type of circadian rhythm disorder are able to set their own schedule, their quality and duration of sleep are normal. Symptoms of this subtype typically begin in adolescence and early adulthood and may continue for months or years before treatment is sought or a diagnosis is made.
- The advanced sleep phase type is characterized by sleep and waking times several hours earlier than are desired or customary. People with this condition may fall asleep two or more hours before their desired sleep time and consequently experience early morning insomnia followed by excessive sleepiness throughout the day. It’s common for individuals with this subtype of circadian rhythm disorder to mistakenly think of themselves simply as “morning people,” as they will persist in waking early even on mornings after they are required to stay up late.
- The shift work type of circadian rhythm sleep-wake disorder is most often diagnosed in those with a history of regularly working outside of the typical 8:00 am–9:00 pm daytime work window. Individuals with this type of circadian rhythm disorder consistently experience excessive sleepiness at work and have difficulty sleeping at home, but the symptoms typically improve or disappear when the person resumes a daytime work routine.
- The irregular sleep-wake type most commonly affects people with neurodegenerative disorders such as Alzheimer’s disease, Parkinson’s disease, or Huntington’s disease. People with this condition have no clear circadian rhythm, and so their sleep is often fragmented into at least three periods during a 24-hour cycle. Those with this type of circadian rhythm disorder typically have insomnia at night and excessive sleepiness or napping during the day; as a result, they do not have one main period of sleep as most people do. This disorder.
- The non-24-hour sleep-wake type of circadian rhythm disorder is most commonly seen among blind or visually impaired people who have decreased light perception. The natural circadian rhythm of those with this condition does not align with the 24-hour day. Such individuals may experience insomnia or excessive sleepiness, depending on the time of day and where their natural circadian rhythm is at that time. They may have periods during which they feel they have no symptoms because their natural sleep phase aligns with conventional sleep times, but these periods tend not to last because their natural sleep phase will drift later into the night until their sleep time again becomes daytime.
No established genetic factors predispose individuals to develop a circadian rhythm sleep-wake disorder, but symptoms of some subtypes, such as advanced sleep phase type, can have an earlier onset and be more severe among people with a family history of such disorders.
Light exposure also plays a role in developing some circadian rhythm disorders. For example, hypersensitivity to evening light may predispose someone to develop the delayed sleep phase subtype.
Treatment options for a circadian rhythm sleep-wake disorder depend on the subtype diagnosed and the impact symptoms have on an individual’s quality of life. Behavior therapy strategies include maintaining consistent sleep-wake times, avoiding naps, exercising regularly, and avoiding stimulating activities and substances like coffee or nicotine near bedtime.
People with delayed sleep phase type should minimize exposure to light in the evening by keeping the lights in their home dim and avoiding bright screens.
Individuals with advanced sleep phase type should increase light exposure in the evenings by keeping lights on in their home.
Bright Light Therapy is one treatment option offered by sleep specialists to advance or delay sleep. Medications such as melatonin and short-term sleep aids can also be used to help adjust sleep-wake time to a desired schedule.