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Circadian Rhythm Sleep Disorders
Delayed Sleep Phase – Advanced Sleep Phase Disorders– Non-24-hour Sleep-wake cycle – Irregular Sleep-Wake Rhythm – Symptoms – Causes – Treatment
Circadian rhythm sleep disorders are caused by mismatch between the internal clocks and the sleep-wake times dictated by society standards and astronomical clocks. As a result, patients suffer chronic sleep disturbance and fatigue. Anxiety and depression are very common in circadian rhythm disorders.
Familial cases are common and are probably related to clock genes variants. Jet-Lag Disorder and Shift Work Sleep Disorder are human-made conditions described in separate articles.
Delayed Sleep-Phase Disorder (going to sleep and wake up late)
Delayed sleep-phase disorder is a chronic disorder of inability to fall asleep and to wake up at socially acceptable times.
Patients typically fall asleep between 1 am and 6 am and wake up in late morning or early afternoon. They are often late for school or work and perform poorly in the mornings. When allowed to sleep at their preferred times they feel perfectly fine.
Genetic factors appear to play some role. Some patients, probably, have longer than normal internal circadian period.
People with this disorder often choose occupations with afternoon and evening working hours. Anxiety and depression are common.
The treatment is a combination of Melatonin and light therapy. Melatonin (0.5 to 5 mg) is given 6 hours prior to regular bed time (or 13 hours after normal wake up time).
Bright light exposure for two hours in the morning hours is recommended. Melatonin was also shown to improve depression in patients with delayed sleep-phase disorder. Once this therapy is discontinued, 90% will revert back to abnormal sleep pattern.
Chronotherapy is a therapeutic option for children. In order to get a sustained effect, rigorous efforts have to be made to adhere to the strict sleep schedule.
Chronotherapy involves delaying bed time by 3 hours each day until the desired sleep time is reached.
Advanced Sleep-Phase Disorder (sleepy in the evening and waking up early)
Advanced sleep-phase disorder is characterized by chronic difficulty staying awake in the late afternoon/evening hours (typically between 6 pm and 9 pm) and early awakening between 2 am and 5 am.
It is much less common than delayed sleep phase disorder. It is typical in middle age and has genetic predisposition.
Depression often has similar sleep pattern and has to be ruled out. Studies suggest that there is an increased sensitivity to light in the morning leading to shortening the circadian period.
Treatment is directed to avoidance of light exposure in the morning hours and increasing in the late afternoon and evening hours.
Melatonin in early morning hours might offer additional benefit.
Irregular Sleep-Wake Rhythm Disorder (irregular fragmented sleep)
This disorder is common adults with dementia (such as Alzheimer’s disease) and patients with developmental disorders. Nursing home residents with sun-downing are especially prone to irregular sleep pattern.
Degeneration of parts of the brain responsible for circadian rhythm generation and lack of structured social responsibilities are the causes. Other factors are lack of sufficient light exposure and eye disorders (e.g. cataracts).
There are multiple 1 to 4 hour naps during 24 hour period without long sleep period at night. Overall number of sleep hours is usually normal.
Melatonin was not shown to be effective as a single agent. Bright light exposure in the morning hours, sufficient darkness at night and structured social and physical activities during the day with or without Melatonin improve sleep-wake cycle in these patients.
Non-24-Hour Sleep-Wake Disorder
Non-24-hour sleep-wake disorder presents with internal circadian rhythms running independently from environmental cues. Sleep cycle in this condition is longer than 24 hours and the person’s sleep time advances each day.
Approximately 50% of blind people have this condition. It is more common in males. Lack of synchronization of internal clocks with day-light cycle is pretty much understandable in people with no light perception.
In sighted people this condition is probably caused by abnormally long internal circadian cycle that prevents adjustments based on the light and social cues.
Patients typically have a few days or weeks of difficulty falling asleep and drowsiness during the day followed by a period of time without any symptoms.
Treatment with high dose of Melatonin (3 to 10 mg) before bed for a few weeks followed by low dose (0.3 mg) thereafter is the best treatment.
In sighted people, additional exposure to bright light in the morning hours offers additional benefits.
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