Non 24 hour Sleep Wake disorder


Tau: an individual’s circadian period is a tau. Light is the strongest stimuli for the synchronization to 24 hours sleep wake cycle. At dim light, melatonin gets released from the pineal gland signaling the body of sleep time.

Disorder: Non 24 is one of the four endogenous circadian rhythm sleep disorder (CRSD). It occurs when the person’s circadian rhythm is not entrained with the environment’s 24 hour sleep wake cycle. Irregular sleep disorder leads to insomnia and daytime sleep.

Symptoms: varies  from patient to patient, and most complaints are of disrupted night time sleep, daytime nap and  irritability.

Diagnosis:  minimal criteria consists of a complaint in  falling asleep or rising up, delayed sleep cycle with a more than 6 weeks of this irregulation. It is most commonly found in blind patients.

Treatment approaches:

  • It is not just a sleep disorder but a circadian rhythm disorder so the therapy or treatment is more complex than just the use of  hypnotics and sedatives.
  • Underlying causes require equal attention and needs to be resolved as well.
  • Light therapy is done for 2-3 hours daily.

 Endogenous CRSD:


Advanced sleep phase disorder A stable sleep schedule several hours earlier than desired normal.
Delayed sleep phase disorder Later than conventional
Irregular sleep wake rhythm Sleep times shortened & randomly distributed throughout the day. Commonly seen  in neurologic impairments.
Non 24 hour sleep wake disorder Sleep cycle shifts in & out of sync.


Pharmacological options:

Drug Dosage Regimen Duration of use
Melatonin 10mg Daily 3-9weeks or more
Tasimelteon 20mg capsules 1 hour before bed time, at the same time every night 6months
Vit B12 500, 1000, 5000mcg 1-3 times daily 5 days-2 years.

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