National Sleep Foundation

Chapter 5: Circadian Rhythm Sleep Disorders

Assessment and Diagnosis

Assessment and diagnosis of Irregular Sleep Wake Type (IST)

Similar clinical assessment is required of all circadian rhythm sleep disorders. As with all suspected sleep disorders, proper assessment of circadian rhythm sleep disorders includes a complete sleep history. Specifically, analysis of the sleep-wake schedule by sleep log or actigraph, for at least 7 days, should be used to uncover potential variations in sleep timing and to rule out other sleep disorders, such as insomnia, that are often mistaken for circadian rhythm sleep disorders.1


  1. Silber MH, Krahn LE, Morgenthaler TI. Circadian rhythm disorders. In: Silber MH, Krahn LE, Morgenthaler TI, eds. Sleep medicine in clinical practice. London, Eng: Taylor and Francis; 2004:253-276.