Speed and direction of shift rotation.

This review paper deals with the issue of shift rotation, i.e. the number of consecutive shifts of the same type and the order of change between shifts. To minimize the disturbances of the circadian system and the accumulation of sleep deficits, rapidly and clockwise-rotating shift systems would seem to be preferable. Regarding consecutive night shifts, a week of night shifts seems to be the worst system with regard to performance and accidents. There is a lack of reliable data on the effects of permanent vs. rotating-shift systems on alertness, performance and accidents. This is also true for the comparison of forward (delaying) and backward (advancing) rotating-shift systems, although the former would seem to be associated with fewer problems. For both systems, controlled longitudinal studies are necessary.