Circadian rhythm sleep disorders is a family of sleep disorders that all involve a problem in the timing of when a person sleeps and is awake. People with circadian rhythm sleep disorders are unable to go to sleep and awaken at the times commonly required for work and school. A person’s internal circadian body clock controls the sleep-wake cycle and functions in a cycle that lasts a little longer than 24 hours. The circadian clock is “set” primarily by visual cues of light and darkness, as well meal and exercise schedules.
Each circadian rhythm sleep disorder involves one of these two problems:
Delayed sleep phase disorder (DSP): This disorder is characterized by a much later than normal timing of sleep onset and offset and a period of peak alertness in the middle of the night. Many times people with this type of disorder are characterized as “evening types” or “night owls”. Teens and young adults are more at risk for DSP.
Advanced sleep phase disorder (ASP): This disorder is characterized by difficulty staying awake in the evening and difficulty staying asleep in the morning. A person with ASP regularly goes to sleep and wakes up several hours earlier than most people. Many times people with this type of disorder are characterized as “early birds” or “morning types”. ASP is more common as people age.
Jet lag disorder: This disorder is a temporary sleep problem that can affect anyone who quickly travels across multiple time zones. In the new time zone the person must sleep and wake at times that are different than his or her own body clock. The severity of the problem increases with the number of time zones that are crossed, and people tend to have more trouble adjusting to eastward travel than to westward travel. Jet lag affects can affect all age groups. Symptoms typically begin approximately one to two days after air travel across at least two time zones.
Shift work disorder: This disorder occurs when a person’s work hours are scheduled during the typical sleep period. Sleepiness during the work shift is common, and trying to sleep during the time of day when most others are awake can be a struggle. This disorder typically affects people working night shifts, early-morning shifts and rotating shifts. Persons with comorbid medical, psychiatric and other sleep disorders such as sleep apnea and individuals with a strong need for stable hours of sleep may be at particular risk.
Irregular sleep-wake rhythm: This disorder is very rare and usually occurs in a person who has a problem with brain function and who does not have a regular routine during the day, or whose sleep-wake cycle that is undefined. The amount of total sleep the person gets is typical, but the body clock loses its normal circadian cycle. The person tends to nap more than usual throughout the day. Sufferers may complain of chronic insomnia, excessive sleepiness or both. A person must have at least three abnormal sleep-wake episodes during a 24-hour period to be diagnosed with this problem. The time between episodes is usually 1 to 4 hours. This disorder is more common in nursing home residents and other people who have little exposure to time cues such as light and social activity.
Free-running (nonentrained) type: This disorder, which is common among people who are blind, occurs when a person’s sleep pattern is not adjusted or entrained to the 24 hour sleep-wake cycle. It shifts later every day. It results most often when the brain receives no lighting cues from the surrounding environment. Occasionally, the disorder is associated with mental retardation or dementia. It has also been suggested that there may be an overlap between circadian rhythm sleep disorder, delayed sleep phase type, and circadian rhythm sleep disorder, free-running type.
Certain lifestyle changes may help people may cope better with certain circadian rhythm sleep disorders by doing such things as adjusting one’s exposure to daylight, making changes in the timing of daily routines, strategically scheduling naps, and developing good sleep hygiene habits.
Additional treatments may include