Abstract

To develop optimal shift systems for an improvement of work schedule satisfaction, health and work productivity, the effects of the direction of the rotational work shifting on the circadian rhythm and adaptation of physiological components and work mistakes were investigated in nursing students. Two groups of seven volunteers participated as experimental subjects, apd seven to twenty nursing students participated as a control group. The directions of rotation work shift were as follows CW(clockwise)-shift system rotation in the direction of day shift(3 days), evening shift(3 days), off duty(l day) and night shift(5 days), and CCW (counterclockwise) -shift system rotation in the reverse direction. Urinary Na, K, and Cl levels were measured with ion-selective electrodes. The levels of performance were measured by a questionnaire to determine the number of mistakes in 12 specific items during duty. The disturbance of Na the circadian rhythm was seen on day and night shifts, especially in the CCW-rotation shift system, and the magnitude of the daily variation was greatest in the CCW-rotation system. The daily rhythms of K and Cl shifted to the right on the evening shift, and the rhythms were reversed on the night shift, which suggests that they adapted to the altered shift work. However, the levels of Cl were higher in day and night shift workers, especially in CCW-shift system. In the ease of urine salts, it seems that the students in CW-shift system more easily adapted to the altered shift. The incidence of mistakes during work were more frequent on the CCW shift than in the CW shift. These data indicate that the direction of rotation effects the worker's health and work performance. These results indicate that the CCW rotation of shift work makes it more difficult for the workers to adapt to the shift on a physiological level, and has many more negative effects on the shift workers' health when compared with the CW rotation. Thus, a clockwise rotating shift system seems to be more desirable for the optimal health and performance of nurses.