Circadian rhythm disturbances and sleep disorders in shift workers.

Employment which requires frequent shift rotation may lead to the development of specific sleep disorders. Delayed sleep phase (DSP) insomnia, a syndrome identified recently, can greatly impair an individual's circadian rhythm-dependent functions; it can occur when shift work disrupts normal sleep-waking schedules. Disorders of excessive daytime sleepiness, such as narcolepsy, occur in some subjects after they have been subjected to frequently rotating shifts. Understanding the problems associated with circadian rhythm disturbances and their interaction with sleep disorders is particularly important in industrial medicine; any clinician whose patients are subjected to frequent shift rotations should consider the effects of disrupted sleep-waking schedules.