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Delayed sleep-phase disorder (DSPD), also known as delayed sleep-phase syndrome (DSPS) or delayed sleep-phase type (DSPT), and in the 2014 revision of the ''International Classification of Sleep Disorders'' (ISCD-3), delayed sleep-wake phase disorder, is a dysregulation of a person's circadian rhythm (biological clock), compared to the general population and relative to societal norms. The disorder affects the timing of sleep, peak period of alertness, the core body temperature rhythm, hormonal and other daily cycles. People with DSPD generally fall asleep some hours after midnight and have difficulty waking up in the morning. They probably have a circadian period significantly longer than 24 hours. Affected people often report that while they do not get to sleep until the early morning, they do fall asleep around the same time every day. Unless they have another sleep disorder such as sleep apnea in addition to DSPD, patients can sleep well and have a normal need for sleep. However, they find it very difficult to wake up in time for a typical school or work day. If they are allowed to follow their own schedules, e.g. sleeping from 3:00 a.m. to 12:00 noon, their sleep is improved and they may not experience excessive daytime sleepiness.〔 Attempting to force oneself onto daytime society's schedule with DSPD has been compared to constantly living with jet lag; DSPD has, in fact, been referred to as "social jet lag".〔 The syndrome usually develops in early childhood or adolescence. An adolescent version may disappear in late adolescence or early adulthood; otherwise DSPD is a lifelong condition. Depending on the severity, the symptoms can be managed to a greater or lesser degree, but there is no known cure. Prevalence among adults, equally distributed among women and men, is approximately 0.15%, or 3 in 2,000. Prevalence among adolescents is as much as 7–16%.〔(【引用サイトリンク】url=http://my.clevelandclinic.org/services/neurological_institute/sleep-disorders-center/disorders-conditions/hic-delayed-sleep-phase-syndrome )〕 DSPD is also genetically linked to ADHD by findings of polymorphism in genes in common between those apparently involved in ADHD and those involved in the circadian rhythm and a high proportion of DSPD among those with ADHD. DSPD was first formally described in 1981 by Elliot D. Weitzman and others at Montefiore Medical Center. It is responsible for 7–10% of patient complaints of chronic insomnia. However, since many doctors are unfamiliar with the condition, it often goes untreated or is treated inappropriately; DSPD is often misdiagnosed as primary insomnia or as a psychiatric condition. DSPD can be treated or helped in some cases by careful daily sleep practices, light therapy, dark therapy, and medications such as melatonin and modafinil (Provigil); the former is a natural neurohormone responsible partly and in tiny amounts for the human body clock. At its most severe and inflexible, DSPD is a disability.〔 A chief difficulty of treating DSPD is in ''maintaining'' an earlier schedule after it has been established, as the patient's body has a strong tendency to reset the sleeping schedule to its intrinsic late times. People with DSPD may improve their quality of life by choosing careers that allow late sleeping times, rather than forcing themselves to follow a conventional 9-to-5 work schedule. ==Definition== According to the International Classification of Sleep Disorders, Revised (ICSD-R, 2001), the circadian rhythm sleep disorders share a common underlying chronophysiologic basis: Incorporating minor updates (ICSD-3, 2014), the diagnostic criteria for delayed sleep-phase disorder are: Some people with the condition adapt their lives to the delayed sleep phase, avoiding morning business hours as much as possible. The ICSD's severity criteria are: * Mild: Two-hour delay (relative to the desired sleep time) associated with little or mild impairment of social or occupational functioning. * Moderate: Three-hour delay associated with moderate impairment. * Severe: Four-hour delay associated with severe impairment. Some features of DSPD which distinguish it from other sleep disorders are: * People with DSPD have at least a normal—and often much greater than normal—ability to sleep during the morning, and sometimes in the afternoon as well. In contrast, those with chronic insomnia do not find it much easier to sleep during the morning than at night. * People with DSPD fall asleep at more or less the same time every night, and sleep comes quite rapidly if the person goes to bed near the time he or she usually falls asleep. Young children with DSPD resist going to bed before they are sleepy, but the bedtime struggles disappear if they are allowed to stay up until the time they usually fall asleep. * DSPD patients usually sleep well and regularly when they can follow their own sleep schedule, e.g., on weekends and during vacations. * DSPD is a chronic condition. Symptoms must have been present for at least three months before a diagnosis of DSPD can be made.〔 Attempting to force oneself onto daytime society's schedule with DSPD has been compared to constantly living with jet lag; DSPD has, in fact, been referred to as "social jet lag". Often people with DSPD manage only a few hours sleep per night during the working week, then compensate by sleeping until the afternoon on weekends. Sleeping late on weekends, and/or taking long naps during the day, may give people with DSPD relief from daytime sleepiness but may also perpetuate the late sleep phase. People with DSPD can be called night owls. They feel most alert and say they function best and are most creative in the evening and at night. People with DSPD 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 those who have DSPD 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. DSPD 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 disorder occurs in childhood and 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 third edition of the International Classification of Sleep Disorders (ICSD-3) is delayed sleep-wake phase disorder. Earlier, and still common, names include delayed sleep-phase disorder (DSPD), delayed sleep-phase syndrome (DSPS) and circadian rhythm sleep disorder, delayed sleep-phase type (DSPT). 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Delayed sleep phase disorder」の詳細全文を読む スポンサード リンク
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