The twenty-four hour workday: proceedings of a symposium on variations in work-sleep schedules. Johnson LC, Texas DI, Colquhoun WP, Colligan MJ, eds. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 81-127, 1981 Jul; :269-288
Research methods for effects of shiftwork (SW) on social and biological functioning of workers were discussed. In a 1979 survey, 23.3 percent of 743,000 Japanese workers were engaged in SW. Fractions of shiftworkers were 70 in mining, 36 in energy supply and hospitals, 23 in manufacturing, and less than 4 percent in finance. Most three/team three/shift systems were of the non weekend work type. Continuous four/team three/shift systems were more popular in manufacturing and power supply industries. Recently more elderly people were scheduled to work in shift systems. In industries that employed young female workers, the tendency was for the double/day system. Of 1426 enterprises studied, 716 of them adopted 1235 shift systems, showing high diversity. The tendency toward diversity was determined primarily by socioeconomic conditions and partially by technical reasons. Major problem areas were work performance, safety, health risks, physiological reentrainment, insufficient sleep, family and social life, and professional relationships. A survey of 2152 daytime and 7964 shift workers indicated that 43.2 percent of male daytime workers, 51.9 of double/day shift workers, 45.6 of three/shift workers, 53.0 of day/night two/shift workers and 52.8 percent of other shift workers were absent due to sickness during a 1 year period. Shiftworkers frequently complained of irregularity of life, rest disturbances, and lack of free time. The Japanese Shift Work Committee identified seven major problem areas of SW: physiological disorders; workload and safety; physical fitness; implications for health; health supervision; social well being; and basic working conditions. Primary objectives in the SW studies were job load analysis and work schedule evaluation. A self reporting method, based on a questionnaire and medical examination, was the most popular method of evaluation. The author recommends that field research studies should deliberately focus on current questions of SW, its problem structure, and local political, custom, and adjustment habits.