交代勤務制が病院看護婦の生理機能に及ぼす影響

とくに深夜勤および勤務間隔時間が短い場合について

抄録

A survey was made on nurses working in a certain university hospital, with regard to night shifts and short off-duty period incorporated in the system. Of the 115 nurses working in the wards studied, 84 were working a three-shift system, 18 a two-shift system and 7 a permanent night shift system. The three-shift system consisted of a day shift (8.30-16.30), an evening shift (16.30-0.30) and a night shift (0.30-8.30), which was performed in a very irregular way with no fixed cycle of rotation. The number of night shifts averaged 10 per month for nurses working by the three-shift system, and 20 for nurses in permanent night duty. According to the rotation schedule, each nurse was obliged to have off-duty periods of about 8 hours about 5 times a month on the average and to work two consecutive night duties once or more a month, while nurses working the permanent night duty had two consecutive services 10.7 times a month. Results of time study of nurses revealed that a large portion of time was spent for contact with patients, either directly looking after them or indirectly assisting medical treatments, and that during most of the duty hours the working posture was either standing, walking, or forward bending. The frequency of fatigue complaints after a shift was higher in the order of day shift < evening shift < night shift. Especially after the night duty, symptoms of drowsiness and dullness and symptoms of difficulty in concentration increased markedly. It was shown that the drowsiness-dullness symptoms were always higher in frequency after a day shift following an off-duty period of 8-hour than that following off-duty hours of 16 or more hours. In the case of a night duty, the fatigue complaints were more frequent after a shift following an 8-hour or 16-hour off-duty period. As for flicker fusion frequency (CFF) and body temperature changes in different shifts, they remained at extremely low levels during a night shift, and especially low between 4.00-6.00 a.m., both CFF and body temperature being elevated afterwards. At the end of a night duty, however, CFF was 2-3 Hz lower than before a day shift. The decrease of the CFF level in the late afternoon of a day-shift was more marked after a shift following an off-duty period of 8-hour than after a shift following longer off-duty hours. In the case of night duty, the lowering rate was in the descending order of 8, 16 and 24 hours of the off-duty period, the CFF level being the lowest between 4.00-6.00 a.m. When the nurses had to take the next shift after a short off-duty period of 8 hours, they were in debt of sleeping hours, which otherwise could be paid off by a following night sleep. Further the meal time of shift workers was very irregular on days of evening- or night-shift, reduction in frequency of meals per day being frequent among them. On the basis of the results obtained, it is concluded that nurses are adversely affected by the frequent short off-duty period and consecutive night shifts and that their shift system should be corrected so as to avoid these conditions.