The circadian system represents a temporal order which is mediated by the mutual coupling of oscillators and by the synchronizing effects of zeitgebers. It is known that well-being of man depends partly on the maintenance of this order, and that
repeated or long lasting disturbances to it such as shift work will cause harmful effects.
This study was a quasi-experimental study to test the effect of shift directions for the clinical nurses on the circadian rhythm. Fourteen nurses working at the general units of Y hospital were selected according to the established criteria.
Fourteen
subjects were assigned to a weekly shift but directions of shift work were phase delay first and then phase advance or vice versa.
Oral temperature, total sleeping time, frequency of sleep-wake, cycle, fatigue, mental performance, and physical symptom were measured during these days except holidays. The data collection period was from April 26, 1993 to July 3, 1993.
MANOVA and Wilcoxon signed rank test were used for statistical analysis.
@ES The results are summarized as follows.
@EN 1. Having worked on evening and night shifts in either phase delay or phase advance schedules, temperature rhythms of shift workers were gradually adapted to the new sleep-wake cycles. A complete adaptation to work on the night shift was
achieved
the sixth day of the night shift in the phase delay schedule compared to the partial adaptation to the work on the night shift in the phase advance schedule. Accordingly, by putting evening shift between day and night shifts, it will be possible
for
circadian rhythm to adapt easily to the night shift.
2. There were differences in the total sleeping time, frequency of sleep-wake cycle, fatigue, and physical symptom except for mental performance between night shift and day, evening shift. This indicates further that shift workers working on the
night
shift have a hard time adapting to the shift work compared to other shifts.
3. Evaluating all the acrophases of temperature rhythm either in phase delay or phase ad-vance schedules, it was shown that night no evening shift in the phase advance schedule revealed the smallest phase move. Also phase advance schedule showed
poorer
adaptation to shift work than phase delay schedule in connection with total sleeping time, frequency of sleep-wake cycle, fatigue, mental performance, and physical symptom.
It is suggested, taken together, these findings reflect that phase delay schedule facilitated the degree of adjustment to the shift work compared to the phase advance schedule.
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