Delayed sleep-phase syndrome is a disorder in which the major sleep episode is delayed in relation to the desired clock time, resulting in symptoms of sleep onset insomnia or difficulty in awakening at the desired time.

Delayed sleep-phase syndrome (DSPS) is marked by: (1) sleep onset and wake times that are later than desired, (2) actual sleep onset times at nearly the same daily clock hour, (3) little or no difficulty in maintaining sleep once sleep has begun, (4) extreme difficulty awakening at the desired time in the morning, and (5) a relatively severe to absolute inability to advance the sleep phase to earlier hours by enforcing normal sleep and wake times. Typically, the patients complain primarily of chronic difficulty in falling asleep until between 2 a.m. and 6 a. m. or difficulty awakening at the desired or necessary time in the morning to fulfill social or occupational obligations. Daytime sleepiness, especially in the morning hours, occurs variably, depending largely on the degree of sleep loss that ensues due to the patient’s attempts to meet his or her social obligations by getting up “on time.” When not obligated to maintain a strict schedule (e.g., on weekends or during vacations), the patient sleeps normally but at a delayed phase relative to local time.

Patients with DSPS are usually perplexed that they cannot find a way to fall asleep more quickly. Their efforts to advance the timing of sleep onset (early bedtime, help from family or friends in getting up in the morning, relaxation techniques, or the ingestion of hypnotic medications) yield little permanent success. Hypnotics in normal doses are often described as having little or no effect at all in aiding sleep onset and may only aggravate the daytime symptoms of difficulty awakening and sleepiness. Chronic dependence on hypnotics or alcohol for sleep is unusual but, when present, complicates the clinical situation. More commonly, patients give a history of having tried multiple sedating agents, which were abandoned because of only transient efficacy.

Patients with DSPS typically score high as “night people” on the owl-lark questionnaire and state that they feel and function best and are most alert during the late evening and night hours. Sleep wake logs obtained during periods when morning social obligations are lessened or absent (vacations, long weekends, unemployment, and school suspension) show fairly consistent, but also consistently “late,” sleep and arising times.

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.” In adolescents, failure to cooperate with a plan to reschedule the patient’s sleep may be a sign of clinical depression.

The duration of DSPS symptomatology varies from months to decades in cases reported in the literature. Adolescence appears to be a particularly vulnerable life stage for the development of the syndrome. However, the histories of some adult patients extend back to early childhood, and pediatric sleep clinicians have described prepubertal children with the syndrome.

Many DSPS patients report that their difficulties began after a period of late night studying or partying, or after employment at an evening or night shift, following which they found it impossible to resume sleeping on a conventional schedule despite the resumption of conventional work or school hours. Prevalence in the general population is unknown. One survey study of adolescents found evidence suggesting 7% prevalence in this age group. There may be individuals who adapt to the pattern by taking evening or night jobs. Adolescence appears to be the most common period of life for the onset of DSPS, but childhood cases have been reported. Onset after age 30 is rare. Sex ratio: 10: 1 male: female.

The cause of DSPS is unclear. Patients with DSPS are thought to have a relatively weak ability to phase advance their circadian systems in response to normal environment time cues (Zeitgebers).

Occupational, school, and social dysfunctions of varying degrees are a typical accompaniment of DSPS and are often the major complaint that brings the patient to clinical attention. Absenteeism and chronic tardiness are poorly tolerated in the school and day-shift work settings, and many patients with DSPS come to be regarded as lazy, unmotivated, or mentally ill by their families, peers, and superiors in the business or school environment, even in the context of otherwise good social and mental functioning. Whether DSPS results directly in clinical depression or vice versa is unknown, but many patients express considerable despair and hopelessness over sleeping normally again. Chronic sedative or alcohol use or abuse accompanies some cases as a complicating feature.

Patients with DSPS should be differentiated from individuals who habitually go to sleep and awaken late for social reasons but then complain of sleep onset insomnia and difficult morning awakening on the sporadic days that they must go to bed and get up early. Such individuals suffer instead from a transient sleep-wake-cycle disturbance, compounded by sleep loss, which usually accompanies an acute-phase shift. Such cases are better categorized as inadequate sleep hygiene. Reestablishment of a regular, more conventional sleep schedule achieves rapid and appreciable success in the transient case, whereas it is ineffective in DSPS.

A chronic pattern of sleep phase delay is sometimes seen in patients with nocturnal panic attacks or in phobic, avoidant, and introverted individuals. With such patients, it may be difficult to decide whether sleeping late represents avoidance of social interaction or a wholly independent process (i.e., DSPS). A history of stable entrainment at earlier, more conventional hours (e.g., at camp, in the military, or during a hospitalization) at any time during the period of DSPS symptoms strongly suggests that the patient has a normal endogenous phase resetting capacity and that DSPS is therefore unlikely.

Another important differentiation is from a non 24 hour sleep wake syndrome in which incremental sequential delays of the sleep phase occur even during periods of vacation or unemployment.

If you suspect Delayed Sleep-Phase Syndrome, please, contact a sleep specialist before learning or occupational problems arise.

Ref: The International Classification of Sleep Disorders