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Delayed sleep phase syndrome
Delayed sleep-phase syndrome (DSPS), also known as delayed sleep-phase disorder (DSPD) or delayed sleep-phase type (DSPT), is a circadian rhythm sleep disorder, a chronic disorder of the timing of sleep, peak period of alertness, hormonal and other rhythms. People with DSPS tend to fall asleep well after midnight and also have difficulty waking up in the morning.
Often, people with the disorder report that they cannot sleep until early morning, but they fall asleep at about the same time every "night", no matter what time they go to bed. Unless they have another sleep disorder such as sleep apnea in addition to DSPS, patients can sleep well, and have a normal need for sleep. Therefore, they find it very difficult to wake up in time for a typical school or work day since they have only slept for a few hours. However, they sleep soundly, wake up spontaneously, and do not feel sleepy again until their next "night" if they are allowed to follow their own late schedule, e.g. sleeping from 4 a.m. to noon.
The syndrome usually develops in early childhood or adolescence, and sometimes disappears in adolescence or early adulthood. It can be to a greater or lesser degree treatable, but cannot be cured.
DSPS was first formally described in 1981 by Dr. Elliot D. Weitzman and others at Montefiore Medical Center. It is responsible for 7 -10% of cases of chronic insomnia. However, as few doctors are aware of its existence, it often goes untreated or is treated inappropriately. DSPS is frequently misdiagnosed as primary insomnia or as a psychiatric condition.
According to the International Classification of Sleep Disorders (ICSD), the key characteristics of DSPS are:
The following features of DSPS distinguish it from other sleep disorders:
Attempting to force oneself through 9–5 life with DSPS has been compared to constantly living with 6 hours of jet lag. Often, sufferers manage only a few hours sleep a night during the working week, then compensate by sleeping until the afternoon on weekends. Sleeping in on weekends, and/or taking long naps during the day, gives people with the disorder relief from daytime sleepiness but also perpetuates the late sleep phase.
People with DSPS tend to be extreme night owls. They feel most alert and say they function best and are most creative in the evening and at night. DSPS patients cannot simply force themselves to sleep early. They may toss and turn for hours in bed, and sometimes not sleep at all, before reporting to work or school. Less extreme and more flexible night owls, and indeed morning larks, are within the normal chronotype spectrum.
By the time DSPS patients seek medical help, they usually have tried many times to change their sleeping schedule. Failed tactics to sleep at earlier times may include relaxation techniques, early bedtimes, hypnosis, alcohol, sleeping pills, dull reading, and home remedies. DSPS patients who have tried using sedatives at night often report that the medication makes them feel tired or relaxed, but that it fails to induce sleep. They often have asked family members to help wake them in the morning, or they have used several alarm clocks. As the syndrome is most common in adolescence, it is often the patient's parents who initiate seeking help, after great difficulty waking their child or teenager in time for school.
As of May 2007, the new International Classification of Sleep Disorders has changed the name from Delayed Sleep Phase Syndrome to Delayed Sleep Phase Disorder.
Using the strict ICSD diagnostic criteria, a random study in 1993 of 7700 adults (aged 18-67) in Norway estimated the prevalence of DSPS at 0.17%. A similar study with 1525 adults (aged 15-59) in Japan estimated its prevalence at 0.13%. At least one study indicated that the prevalence of DSPS among adolescents is as high as 7%; among adolescents, boys predominate while the gender distribution shows equal numbers of men and women in adults.
DSPS is a disorder of the body's timing system - the biological clock. Individuals with DSPS might have an unusually long circadian cycle, or might have a reduced response to the re-setting effect of light on the body clock.
People with normal circadian systems can generally fall asleep quickly at night if they slept too little the night before. Falling asleep earlier will in turn automatically advance their circadian clocks. In contrast, people with DSPS are unable to fall asleep before their usual sleep time, even if they are sleep-deprived. Research has shown that sleep deprivation does not reset the circadian clock of DSPS patients, as it does with normal people.
People with the disorder who try to live on a normal schedule have difficulty falling asleep and difficulty waking because their biological clocks are not in phase with that schedule. Normal people who do not adjust well to working a night shift have similar symptoms.
People with the disorder also show delays in other circadian markers, such as melatonin-secretion and the core body temperature minimum, that correspond to the delay in the sleep/wake cycle. Sleepiness, spontaneous awakening, and these internal markers are all delayed by the same number of hours. Non-dipping blood pressure patterns are also associated with the disorder when present in conjunction with socially unacceptable sleeping and waking times.
In most cases, it is not known what causes the abnormality in the biological clocks of DSPS patients. DSPS tends to run in families and a growing body of evidence suggests that the problem is associated with the hPer3 (human period 3) gene. There have been several documented cases of DSPS and non-24 hour sleep-wake syndrome developing after traumatic head injury.
There have been a few cases of DSPS developing into non 24-hour sleep-wake syndrome, a more severe and debilitating disorder in which the individual sleeps later each day.
DSPS is diagnosed by a clinical interview, actigraphic monitoring and/or a sleep log kept by the patient for at least three weeks. When polysomnography is also used, it is primarily for the purpose of ruling out other disorders such as narcolepsy or sleep apnea. If a person can, on her/his own with just the help of alarm clocks and will-power, adjust to a daytime schedule, the diagnosis is not given.
DSPS is frequently misdiagnosed or dismissed. It has been named as one of the sleep disorders most commonly misdiagnosed as a primary psychiatric disorder. DSPS is often confused with psychophysiological insomnia, depression, psychiatric disorders such as schizophrenia, ADHD or ADD, other sleep disorders, or willful behaviour such as school refusal. Practitioners of sleep medicine point out the dismally low rate of accurate diagnosis of the disorder, and have often asked for better physician education on sleep disorders.
Impact on patients
Lack of public awareness of the disorder contributes to the difficulties experienced by DSPS patients, who are commonly stereotyped as undisciplined or lazy. Parents may be chastised for not giving their children acceptable sleep patterns, and schools rarely tolerate chronically late, absent, or sleepy students and fail to see them as having a chronic illness.By the time DSPS sufferers receive an accurate diagnosis, they often have been misdiagnosed or labelled as lazy and incompetent workers or students for years. Misdiagnosis of circadian rhythm sleep disorders as psychiatric conditions causes considerable distress to patients and their families, and leads to some patients being inappropriately prescribed psychoactive drugs. For many patients, diagnosis of DSPS is itself a life-changing breakthrough.
Treatment for DSPS is specific. It is different from treatment of insomnia, and recognizes the patient's ability to sleep well while addressing the timing problem.
Before starting DSPS treatment, patients are often asked to spend a week sleeping regularly, without napping, at the times when the patient is most comfortable. It is important for patients to start treatment well-rested.
Treatments that have been reported in the medical literature include:
Once the patient has established an earlier sleep schedule, following highly regular sleep/wake times and practicing good sleep hygiene are essential. DSPS patients are counselled to not go to bed if they are not sleepy, as doing so generally does not result in earlier sleep times. They are also advised to avoid alcohol and caffeine before bedtime.
With treatment, some people with DSPS can sleep and function well with the early sleep schedule. Stimulant drugs (including caffeine) to keep the person awake during the day may not be necessary. A chief difficulty of treating DSPS is in maintaining an earlier schedule after it has been established. Inevitable events of normal life, such as staying up late for a celebration or having to stay in bed with an illness, tend to reset the person's sleeping schedule to late times again.
Adaptation to late sleeping times
Long-term success rates of treatment have not been evaluated. However, experienced clinicians acknowledge that DSPS is extremely difficult to treat.
Working the evening or night shift, or working at home, make DSPS less of an obstacle for some. Many of these people do not think of describing their pattern as a "disorder." Some DSPS individuals nap, even taking four hours of sleep a day and four at night. Some DSPS-friendly careers include security work, work in theater, the entertainment industry, the media, work in hospitality such as restaurants, hotels, bars, freelance writing, call center work, nursing, and taxi or truck driving.
Some people with the disorder are unable to adapt to earlier sleeping times, even after many years of treatment. Sleep researchers have proposed that the existence of untreatable cases of DSPS be formally recognized as a "sleep-wake schedule disorder disability".
Rehabilitation for DSPS patients includes acceptance of the condition, and choosing a career that allows late sleeping times. In a few schools and universities, students with DSPS have been able to arrange to take exams at times when their concentration is good.
DSPS and depression
In the DSPS cases reported in the literature, about half of the patients have suffered from clinical depression or other psychological problems. The relationship between DSPS and depression is unclear. The fact that half of DSPS patients are not depressed indicates that DSPS is not merely a symptom of depression. Even in depressed patients, treatment methods such as chronotherapy can be effective without directly treating the depression.
According to the ICSD, "Although some degree of psychopathology is present in about half of adult patients with DSPS, there appears to be no particular psychiatric diagnostic category into which these patients fall. Psychopathology is not particularly more common in DSPS patients" compared with others complaining of "insomnia".
It is conceivable that DSPS often has a major role in causing depression, because it can be such a stressful and misunderstood disorder. A direct neurochemical relationship between sleep mechanisms and depression is another possibility.
DSPS patients who also suffer from depression should seek treatment for both problems. There is some evidence that effectively treating DSPS can improve the patient's mood and make antidepressants more effective. In addition, treatment for depression can make patients more able to successfully follow DSPS treatments.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Delayed_sleep_phase_syndrome". A list of authors is available in Wikipedia.|