Interindividual differences in circadian fatigue patterns of shift workers.

Ostberg, 0. (1973). BritishJournalofIndustrialMedicine,30,341-351. Interindividual differences in circadian fatigue patterns of shift workers. Data from 37 computer operators and outputhandlers, 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 diTerences in the workers' circadian patterns of activity, sleep, oral temperature, time estimation, physical fitness, and food intake. By means ofa questionnaire on preferences and habits of activity and time of day, three subgroup3 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 x 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 x shift.