Interindividual differences in circadian fatigue patterns of shift workers

Abstract

Östberg, O. (1973).British Journal of Industrial Medicine,30, 341-351. Interindividual differences in circadian fatigue patterns of shift workers. Data from 37 computer operators and output-handlers, working on discontinuous 8-16-24 alternating shifts, were collected in the morning, evening, and night shifts during a one-year period. The study was directed to the interindividual differences in the workers' circadian patterns of activity, sleep, oral temperature, time estimation, physical fitness, and food intake. By means of a questionnaire on preferences and habits of activity and time of day, three subgroups of five subjects each were selected—`morning', `middle', and `evening' groups. Significant differences were found between the groups and between the shifts. Most interesting was the significant interaction of group × shift, on the basis of which it could be concluded that the `morning' type of subjects had the most pronounced difficulty in adapting to the shift system practised. It is thought that a refinement of the questionnaire used should eventually result in a tool for assessing a person's circadian type and the interaction of type × shift.