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KMID : 0376619930180010012
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Seoul Journal of Psychiatry
1993 Volume.18 No. 1 p.12 ~ p.25
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The Effects of Counterclockwise and Clockwise Shift Work Schedules on the Sleep-Wake Variables and the Body Temperature Rhythm
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Abstract
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The authors tried to compare the effects of two different shift work schedules(counterclockwise vs. clockwise) on the sleep-wake variables and the body temperature rhythm during the adjustment period after the completion of each schedule Eleven
nurses
working in psychiatric inpatient units of Seoul National University Hospital volunteered as study subjects. Counterclockwise(CCW) rotating shift work schedule(three day shifts, three night shifts, and three evening shifts) was followed by 48-hour
adjustment period, in which each subject's sleep-wake rhythm was monitored with the ambulatory wrist activity and light exposure monitor. The same procedure was repeated for each subject after the clockwise (CW) rotating shifts(three evening
shifts,
three night shifts, and three day shifts) which followed CCW schedule 0ne to four weeks after. Within each adjustment period, body temperatures were measured repeatedly every two hours with oral mercury thermometer during wake period. In
addition,
the
sleep questionnaire and the Horne and Ostberg's "morningness-eveningness" questionnaire(Korean version)were used All the data were collected during three month period starting from September 1, 1992. For statistical analysis, wilcoxon
matched-pairs
signed-rank test was used with p walue of 0.1 adopted as cutoff value for significance.
The results were as follows : 1) sleep latency in the first major sleep of the adjustment period following CW shifts was found to be significantly reduced, compared to the one following CCW shifts(p=0.04 ; 2) number of awakenings in the second
major
sleep following CW shifts was significantly less than after CCW shifts(p=0.09);3) wake time after sleep onset in the second major sleep following CW shifts was significantly less after CCW shifts(p=0.07) ;4) comparison of the major sleep periods
during
adjustment revealed no significant differences between two schedules regarding length of sleep ; 5) relative phase delay of the peak body temperature was noted during adjustment after CCW shifts, compared with CW shifts.
In conclusion, this study suggests that CW shift work schedule may enhance more efficiently the adjustment of sleep-wake rhythm than CCW shifts.
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KEYWORD
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