The non-24-hour sleep-wake disorder is an uncommon circadian rhythm sleep disorder.



(1) abnormal circadian sleep rhythm

(2) sleep cycle usually more than 24 hours but may be less

(3) failure to change sleep habits is associated with insomnia and/or excessive sleepiness

(4) abnormal circadian rhythm for melatonin and/or body temperature

(5) improvement following appropriate therapy


It has been referred to as the free running sleep disorder because it resembles the sleep pattern seen in people in isolation with no external time cues (time-free environment).


A person who tries to adapt to the non-24-hour cycle may go to bed later and later and get up later and later. This can interfere with work or other activities.



(1) blindness with no light perception

(2) head trauma

(3) other neurologic disorders affecting the visual system and/or hypothalamus

(4) psychiatric disorder

(5) idiopathic


Therapy may include:

(1) oral melatonin

(2) light therapy (if sighted)

(3) oral vitamin B12


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