著者

松本 一弥 斎藤 良夫 松井 知子 川森 正夫

出版者

公益社団法人日本産業衛生学会

雑誌

産業医学 (ISSN:00471879)

巻号頁・発行日

vol.22, no.3, pp.184-193, 1980-05-20

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The present survey was carried out on the service of guards in the form of night duty in the shift system in order to elucidate the problems involved. Number of subjects was 148. Out of these, 85 worked under the alternate-day shift system whose average age was 42 years, 47 worked under the permanent night duty system of average age of 50 years, and the remaining 16 were on the normal duty of the average age of 45 years. Under the alternate-day shift system, the portal-to-portal time is 24 hours from 10:00a.m. to the same time of the next day from which about 3.O-3.5 hours are exempted for taking a nap. In the permanent night duty it is from 18:00 or 19:00 to 09:00 or 10:00 of the next day, the portal-to-portal ranging 13-16 hours, usually 15-16 hours. The normal duty covers 8 or 9 hours from 10:00 to 17:00 or 18:00, but with incidental night duty of several hours per month. The problems of the alternate-day shift system and of the permanent night duty system were as follows: (1) Under those two systems, the total monthly portal-to-portal time was 312 hours with additional overtime, the mean becoming 397 hours a month in the alternate-day shift system and 405 hours in the permanent night duty system. These are considerably longer than the working time (249 hours) of the normal duty. (2) As for the frequency of the consecutive night shift, it occurred more than twice at the rate of 23% a month in the alternate-day shift system, and some experienced even 7 consecutive night shifts. Under the permanent night duty system, night duty occupied the greatest part in a month (97%), 3 to 5 consecutive night duties being most usual with an exceptional case of 19 consecutive night duties. (3) Number of night duties per month is 16.1 per month on the average under the alternate-day shift system, while 23.2 under the permanent night duty system. (4) The incidence of the spell of the portal-to-portal exceeding 24 hours was 43% per month under the alternate-day shift system. The longest was 72 hours. Under the permanent night duty system, the incidence of the spell of 19 hours or more was about 15%, and the spell of 24 hours or more occurred at the rate of 9%. (5) From the shift formation point of view, the interval between the preceeding or succeeding spell was sometimes null, but it was usually 8-10 hours. The incidence of the former per month was 4.7 times under the alternate-day shift system and 2.7 times under the permanent night duty system. Incidences of the latter under the two systems were 2.0 and 15.1 times, respectively. (6) Number of holidays per month was 3.0 under the alternate-dayshift system, and, 1.1 under the permanent night duty system. Under the normal duty system, it was 4.6. (7) Number of sick absenteeism with medical certificate was 13 in a year (15.3% of the total employees) under the alternate-day shift system, and 7 (14.9% of the total) under the permanent night duty system. As regards diseases which were the reason of absenteeism, 6 were circulatory, 4 respiratory, 4 digestive, each 1 was musculoskeletal, of connective tissue, hepatic, hemopoietic and mental. Except one patient suffering from a respiratory disease and another suffering from a musculoskeletal disease, all were aged 40 years or over. Under the normal duty system there was no sick absenteeism. (8) Number of workers retired in the past one year was 30 under the alternate-dayshift system, 43 under the permanent night duty system, and 1 under the normal duty system. Ratios of the number of retired workers against those in service were 35, 91 and 6% under the three systems, respectively. In the alternate-day shift and permanent night duty systems, and especially in the latter, the number of retired workers tended to be larger among the middle- and old aged. From these results the following items were considered important: Introduction of such countermeasures as reasonably controlling the total work hours, decrease in the number of days of night duty, reor