National Sleep Foundation

Chapter 5: Circadian Rhythm Sleep Disorders

What is Shift Work Disorder?

The circadian rhythm sleep disorder, shift work type (or shift work disorder), is characterized by complaints of insomnia or excessive sleepiness as a result of a work schedule that takes place during the normal sleep period. Shift-work schedules include late evening, night, very early morning, and rotating shifts. Total sleep time is often reduced by 1 to 4 hours in shift workers, even after apparently successful habituation to shift work.1


  1. American Academy of Sleep Medicine. The international classification of sleep disorders: diagnostic and coding manual. 2nd ed. Westchester, Ill: American Academy of Sleep Medicine; 2005.