Circadian rhythms and bright light: Recommendations for shift work

This paper starts with a brief review of the basic principles of human circadian rhythms relevant to understanding the problem of shift work. It then presents a more detailed critical review of the recent bright light literature, with an emphasis on methodological shortcomings, alternative interpretations, and areas that need further research. Evidence is presented which suggests that either a light-dark cycle (which includes bright light) or a sleep-wake schedule can act as a zeitgeber for human circadian rhythms. Current human phase response curves to bright light are reviewed. Light-work-sleep schedules are presented which have been designed to eliminate the physiologically based harmful consequences of shift work. These schedules include both bright light and sleep-wake schedule zeitgebers. Other practical applications of bright light treatment are mentioned.