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Blog Feature

By: Peter Mansbach, Ph.D. on October 11th, 2019

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Circadian Rhythm Sleep Disorders: An Overview

Sleep Disorders | Research | Circadian Rhythms

Circadian rhythm sleep disorders (CRSDs) are neurological disorders in which the sleep-wake cycle is out of sync with the day-night cycle. This article focus on three: delayed sleep phase disorder, advanced sleep phase disorder and non-24-hour sleep-wake disorder.

Delayed sleep phase disorder (DSPD) is characterized by an inability to fall asleep until very late at night, with the resulting need to sleep late in the morning or into the afternoon. Advanced sleep phase disorder (ASPD) is the opposite. It is characterized by falling asleep very early in the evening and waking up in the very early morning hours, unable to sleep further. Non-24-hour sleep-wake disorder (non-24) (also called free running disorder) is a condition in which a person’s day length is significantly longer than 24 hours, so that sleep times get later each day, cycling around the clock in a matter of days or weeks.

A careful survey of 10,000 adults concluded that 0.17% had clinically diagnosable DSPD. That’s about one in 600, or half a million Americans. Three times as many as have narcolepsy. Yet it often goes undiagnosed, in part because people, even doctors, are unaware of these disorders.

The same survey didn’t find any cases of ASPD. Additionally, ASPD is less frequently diagnosed because it doesn’t cause patients to be late for work or school, so they are less likely to seek medical help.

It is estimated that over half of all totally blind people have non-24. However, some sighted people also suffer from non-24. Sighted non-24 was thought to be extremely rare, but our own survey and discussions on social networks suggest it is more common than previously thought.

The first hurdle for people suffering from constant tiredness is to get their primary care doctor to refer them to a sleep specialist. Too often the primary doctor treats the problem as insomnia and prescribes sleeping pills or blames it on depression when the real culprit is the underlying circadian disorder. 

Treatment attempts to shift the patient’s circadian rhythm to fit conventional job schedules. Three treatments are generally suggested: light therapy, light restriction and melatonin.

You can read the whole article in the Q3 issue of A2Zzz

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