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Overview of circadian sleep-wake rhythm disorders

James K Wyatt, PhD
Section Editor
Cathy A Goldstein, MD
Deputy Editor
April F Eichler, MD, MPH


The intrinsic circadian timekeeping system influences consolidation of sleep and wake episodes and is critical for sleep health as well as optimal functioning of other organ systems.

Desynchrony between the internal circadian timing system and desired sleep-wake times can result in one of six circadian sleep-wake rhythm disorders and is also an important factor to consider for most of the other sleep disorders. For example, persistent excessive daytime sleepiness in a patient with treated obstructive sleep apnea may be due to an underlying circadian rhythm sleep-wake disorder as opposed to refractory symptoms despite positive airway pressure therapy.

This topic provides an overview of the pathophysiology, clinical features, and diagnostic criteria of the circadian sleep-wake rhythm disorders. The classification and diagnosis of other types of sleep disorders are presented separately. (See "Classification of sleep disorders".)


The intrinsic circadian timekeeping system modulates many physiological systems, including daily rhythms in core body temperature, cortisol, and appetite [1-3]. The circadian system also actively drives wakefulness during the habitual waking day, helping to offset the progressive increase in sleepiness from the sleep homeostatic system, which accumulates sleep pressure across extended wakefulness [4-6].

Sleep homeostatic drive accumulates during wakefulness and promotes the initiation of sleep. After the first half of the sleep episode, this sleep drive rapidly diminishes. A properly-aligned circadian system increases drive for sleep at night, particularly in the latter half of the night, helping to maintain sleep consolidation until normal wake-up time (figure 1) [7].

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Literature review current through: Nov 2017. | This topic last updated: Sep 02, 2016.
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