Delayed sleep-phase syndrome

Delayed sleep-phase syndrome (DSPS) is a chronic, fairly common, disorder of sleep timing. People with DSPS tend to fall asleep at very late times, and also have difficulty waking up in time for normal work, school, or social needs. DSPS is treatable, but cannot be cured. It is often mistaken for other types of insomnia, and treated inappropriately. The condition usually emerges in adolescence.

Studies indicate that it is responsible for 7 -10% of cases of chronic insomnia.

DSPS treatments are meant to adjust a person’s circadian rhythm and sleep pattern. The goal of treatment is to fit the sleep pattern into a schedule that can allow the person to meet the demands of a desired lifestyle. Treatment is meant to allow the person with DSPS to wake up at a given time feeling refreshed and functional. People receiving treatment gradually adjust to an earlier bedtime with sleep therapy. This therapy usually combines proper sleep hygiene practice and external stimulus therapy such as bright light therapy and chronotherapy.

Epidemiology

Various studies show that DSPS is an uncommon disorder, affecting roughly 5-10% of patients that suffer from insomnia. According to the American Academy of Sleep Medicine, a study showed that there is 7% prevalence of DSPS among adolescents. Signs and symptoms of DSPS start during early childhood or adolescence and may disappear in adolescence or early adulthood. DSPS is equally distributed among both sexes and it not linked to any familial patterns. DSPS usually begins after a change in the normal sleeping pattern. Patients usually report that they had previously stayed up nights; for example studying or taking night shifts. DSPS has also been reported by inhabitants of latitudes above the Artic Circle due to changes in their photo-period.

Pathology

The sleep-wake cycle, skin temperature, and hormones secretions are generated in 24-hour cycles, which is known as the circadian rhythm or the biological clock. The circadian rhythm is controlled by the SupraChiasmatic Nuclei (SCN) in the brain. Most of the time, the circadian rhythm is follows the 24-hour day-night schedule. Sometimes the circadian rhythm of the sleep-wake cycle is out of phase with the usual or desired sleep-wake schedule. This could be due to a lesion to the SCN, other neurological diseases, environmental changes, frequent travels or shift work. In DSPS, there is a rather low ability to phase advance the circadian system in response to the normal environmental time prompts.

Presentation

DSPS patients are usually mind-boggled and simply can not find a way to easily fall asleep. DSPS sufferers try several tactics to fall asleep but are usually in vain. This includes trying to go to sleep early, setting several alarm clocks to go off in the morning, getting others to wake them in the morning and the use of sedatives or hypnotics. When tracking the sleep-wake patterns of patients, the following is spotted; falling asleep after 2 am, many hours of sleep once they have fallen asleep, waking up late during the day and oversleeping during the weekends. Patients with DSPS, or “night people”, mostly state that they are at their optimal performance at night.

In about half of adult patients, psychiatric problems may be present to some extent. It should also be noted that adolescents suffering from DSPS that fail to cooperate in resetting their sleep schedules may indicate the presence of clinical depression. The severity of DSPS is classified into mild, moderate or severe based on the number of hours it takes to fall asleep and its impact on social or occupational functioning- patients usually present with absenteeism and are noted by their families to be lazy and lack motivation.

Actigraphy and DSPS

"Dawn is when men of reason go to bed" - Ambrose Bierce - The Devil's Dictionary.

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