Circadian rhythm sleep disorders: pathophysiology and treatment.

The prediction that abnormalities of circadian clock function in humans would manifest principally as sleep/wake disruption led to the description of the first circadian sleep/wake disorders almost 20 years ago. Since then, formal classification of sleep pathology has expanded this category to include six specific disorders. In this review, the physiology of mammalian circadian clocks is summarized with emphasis on the role of light and hormonal signals in circadian adjustment and entrainment. Each of the circadian sleep disorders-time zone change (jet lag) syndrome, shift work sleep disorder, irregular sleep/wake pattern, delayed sleep phase syndrome, advanced sleep phase syndrome, and non-24-h sleep wake disorder-is reviewed. Presenting characteristics, approaches to diagnosis, models of pathophysiology, and methods of treatment are summarized for each sleep disorder. Developments in the understanding of circadian physiology offer promise for important advances in the diagnosis and treatment of these sleep disorders.