Delayed sleep phase syndrome Classification and external resources |
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ICD-10 | G47.2 |
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ICD-9 | 327.31 |
eMedicine | neuro/655 |
MeSH | D021081 |
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, core body temperature, hormonal and other daily rhythms relative to the usual norms. People with DSPS tend to fall asleep some hours after midnight and 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. If, however, they are allowed to follow their own schedule, e.g. sleeping from 4 a.m. to noon, they sleep soundly, awaken spontaneously, and do not feel sleepy again until their next "night".
The syndrome usually develops in early childhood or adolescence,[1] and sometimes disappears in adolescence or early adulthood. It can be to a greater or lesser degree treatable depending on the severity, but has not yet been found to be fully curable. Prevalence among adults, equally distributed among women and men, is approximately 0.15% or three in 2000 (see below).
DSPS was first formally described in 1981 by Dr. Elliot D. Weitzman and others at Montefiore Medical Center.[2] It is responsible for 7–10% of cases where patients complain of chronic insomnia.[3] 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.[4]
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According to the International Classification of Sleep Disorders (ICSD),[5] the circadian rhythm sleep disorders share a common underlying chronophysiologic basis:
The major feature of these disorders is a misalignment between the patient's sleep pattern and the sleep pattern that is desired or regarded as the societal norm.... In most circadian rhythm sleep disorders, the underlying problem is that the patient cannot sleep when sleep is desired, needed or expected.
The ICSD (page 128-133) diagnostic criteria for Delayed Sleep-Phase Syndrome are:
- There is an intractable delay in the phase of the major sleep period in relation to the desired clock time, as evidenced by a chronic or recurrent complaint of inability to fall asleep at a desired conventional clock time together with the inability to awaken at a desired and socially acceptable time.
- When not required to maintain a strict schedule, patients will exhibit normal sleep quality and duration for their age and maintain a delayed, but stable, phase of entrainment to local time.
- Patients have little or no reported difficulty in maintaining sleep once sleep has begun.
- Patients have a relatively severe to absolute inability to advance the sleep phase to earlier hours by enforcing conventional sleep and wake times.
- Sleep-wake logs and/or actigraphy monitoring for at least two weeks document a consistent habitual pattern of sleep onsets, usually later than 2 a.m., and lengthy sleeps.
- Occasional noncircadian days may occur (i.e., sleep is "skipped" for an entire day and night plus some portion of the following day), followed by a sleep period lasting 12 to 18 hours.
- The symptoms do not meet the criteria for any other sleep disorder causing inability to initiate sleep or excessive sleepiness.
- If any of the following laboratory methods is used, it must demonstrate a delay in the timing of the habitual sleep period: 1) Twenty-four-hour polysomnographic monitoring (or by means of two consecutive nights of polysomnography and an intervening multiple sleep latency test), 2) Continuous temperature monitoring showing that the time of the absolute temperature nadir is delayed into the second half of the habitual (delayed) sleep episode.[5]
Some people with the abnormality adapt their lives to the delayed sleep phase, avoiding common business hours (e.g., 9 a.m. to 5 p.m.) as much as possible. They have the disorder, but for them it is not a disability. The ICSD's severity criteria, all of them "over at least a one-month period", are:
Some features of DSPS which distinguish it from other sleep disorders are:
Attempting to force oneself onto daytime society's schedule with DSPS has been compared to constantly living with 6 hours of jet lag; the disorder has, in fact, been referred to as "social jet lag".[6] 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, may give people with the disorder relief from daytime sleepiness but may also perpetuate 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 maintaining proper sleep hygiene, 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 in time for school.
The current formal name established in the second edition of the International Classification of Sleep Disorders is circadian rhythm sleep disorder, delayed sleep phase type; the preferred common name is delayed sleep-phase disorder.[7]
About three adults of 2000 have DSPS. 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%.[8] A similar study of 1525 adults (aged 15-59) in Japan estimated its prevalence at 0.13%.[9]
At least one study has 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 women and men in adults.[5]
A marked delay of sleep patterns is a normal feature of the development of adolescent humans. According to Mary Carskadon, both circadian phase and homeostasis, the accumulation of sleep pressure during the wake period, contribute to a DSPS-like condition in post-pubertal as compared to pre-pubertal adolescents.[10]
DSPS is a disorder of the body's timing system - the biological clock. Individuals with DSPS might have an unusually long circadian cycle, might have a reduced response to the re-setting effect of daylight on the body clock and/or may respond overly to the delaying effects of evening light and too little to the advancing effect of light earlier in the day.
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 help to advance their circadian clocks due to decreased light exposure in the evening. 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.[11]
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 (diagnosed as shift-work sleep disorder, SWSD).
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. The timing of 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,[12] and a growing body of evidence suggests that the problem is associated with the hPer3 (human period 3) gene.[13][14] There have been several documented cases of DSPS and non-24 hour sleep-wake syndrome developing after traumatic head injury.[15][16]
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.[17] It has been suggested that, instead of (or perhaps in addition to) a reduced reaction to light in the morning, an abnormal over-sensitivity to light in the late evening might contribute to the odd entrainment pattern.[18]
DSPS is diagnosed by a clinical interview, actigraphic monitoring and/or a sleep diary 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.[19] 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.[20]
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.[21] | ” |
As DSPS is so little known and so misunderstood, support groups may be important for information and self-acceptance.[22]
Treatment, perhaps better referred to as a set of management techniques, is specific to DSPS. It is different from treatment of insomnia, and recognizes the patients' ability to sleep well on their own schedules, while addressing the timing problem. Success, if any, may be partial; for example, a patient who normally awakens at noon may only attain a wake time of 10 or 10:30 with treatment and follow-up. Being consistent with the treatment is paramount.
Before starting DSPS treatment, patients are often asked to spend at least 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 a patient has established an earlier sleep schedule, it is absolutely essential to follow highly regular sleep/wake times and to practice good sleep hygiene. With treatment, some people with mild DSPS may sleep and function well with the early sleep schedule. Caffeine and other stimulant drugs to keep a person awake during the day may not be necessary, and should be avoided in the afternoon and evening, as per good sleep hygiene. 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 sleeping schedule to its intrinsic late times.
Long-term success rates of treatment have seldom been evaluated. However, experienced clinicians acknowledge that DSPS is extremely difficult to treat. One study of 61 DSPS patients with mean sleep onset at about 3 a.m. and mean waking time of about 11:30 a.m., followed up with questionnaires to the subjects a year later. Good effect was seen during the 6-week treatment with a daily, very large dose (5mg), of melatonin. Follow-up showed that over 90% had relapsed to pretreatment sleeping patterns within the year, 28.8% reporting that the relapse occurred within one week. The milder cases retained changes significantly longer than the more severe cases.[30]
Working the evening or night shift, or working at home, makes DSPS less of an obstacle for some. Many of these people do not describe their pattern as a "disorder." Some DSPS individuals nap, even taking 4-5 hours of sleep in the morning and 4-5 in the evening. DSPS-friendly careers can include security work, work in theater, the entertainment industry, the media, freelance writing, call center work, nursing, taxi or truck driving and hospitality work in restaurants, hotels or bars.
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 of day when their concentration levels may be good.
“ | Patients suffering from SWSD disability should be encouraged to accept the fact that they suffer from a permanent disability, and that their quality of life can only be improved if they are willing to undergo rehabilitation. It is imperative that physicians recognize the medical condition of SWSD disability in their patients and bring it to the notice of the public institutions responsible for vocational and social rehabilitation.[21] | ” |
In the DSPS cases reported in the literature, about half of the patients have suffered from clinical depression or other psychological problems, about the same proportion as among patients with chronic insomnia.[5] 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 to patients with other forms of "insomnia." ... Whether DSPS results directly in clinical depression, or vice versa, is unknown, but many patients express considerable despair and hopelessness over sleeping normally again.[31] | ” |
It is conceivable that DSPS often has a major role in causing depression, because it can be such a stressful and misunderstood disorder. A recent study from the University of California, San Diego found no association of bipolar disorder (history of mania) with DSPD, and it states that there may be
“ | behaviorally-mediated mechanisms for comorbidity between DSPD and depression. For example, the lateness of DSPD cases and their unusual hours may lead to social opprobrium and rejection, which might be depressing...[32] | ” |
A direct neurochemical relationship between sleep mechanisms and depression is another possibility.
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.
DSPS patients who also suffer from depression may be best served by seeking 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.
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