Field Studies of Shiftwork: II Temporal Patterns in Psychophysiological Activation in Workers Alternating Between Night and Day Work∗

Thirteen male typesetters working a weekly rotating day-night shift schedule were studied with respect to circadian variations of catecholamine excretion, oral temperature, self-rated alertness and choice reaction time. Measurements were made in the beginning, middle and end of the night week and during the beginning of the day week. The catecholamine values during night work indicated low levels of arousal without variation over time for oral temperature and alertness circadian variation was pronounced with very late peaks. No significant variation over time was found for choice reaction time. Tendencies towards adjustment (increase) over the night week were seen for catecholamine excretion, body temperature and self-rated alertness. The results were compared with values for permanent nightworkers and it was found that the latter showed high arousal during night work and no adjustment over the night week, i.e. results indicating long term adjustment to night work. It was concluded that the two-shift workers exhibited in comparison a considerable lack of long term adjustment to night work It was suggested that this lack of adjustment probably is caused by the change in time cues which confront the worker on the alternating shift schedule as opposed to the relative stability of time cues found on the permanent night shift. Results from questionnaire data also suggested that the change from night to day shift may cause as much discomfort as a change in the other direction.