Re-entrainment of body temperature in field studies of shiftwork

Re-entrainment to nightwork appears to be slower in field studies than in experimental shiftwork studies, which might be explained by the influence of unshifted social “Zeitgebers” in real life.

Abstract

Oral temperature readings were taken from six groups of shift-workers (n = 133). The measurements covered a total of 387 days and included readings on a day off and on days of the 1st, 2nd, 4th, 5th and 7th nightshift. The shiftworkers were asked to record oral temperature every 2 h, at work and at leisure, using special thermometers (1°C equals 4 cm). Some of them also interrupted their sleep for additional measurements. On the first day of the night shift the normal circadian rhythm of body temperature was virtually unchanged in most of the groups. However in two groups with a higher physical load during nightwork, an increased temperature was observed during the night ("masking effect"). There were no significant differences between the temperature rhythms in experienced (≥ 15 years of shiftwork) and inexperienced shiftworkers (≤ 1 year of shiftwork) within the first nightshift. During the period of consecutive nightshifts no clear re-entrainment of body temperature was observed. Re-entrainment to nightwork appears to be slower in field studies than in experimental shiftwork studies, which might be explained by the influence of unshifted social "Zeitgebers" in real life.