[Studies on fatigue and shift work in nurses].

Effects of shift work on physiological parameters and autonomic nervous-adrenal system were studied on six hospital nurses. Their body temperature, heart rate, blood pressure, fluctuation in ECG R-R intervals, serum catecholamines and cortisol, and subjective fatigue ratings before and after day, evening and night shift were determined. Furthermore, mean heart rates, walk steps, estimated energy expenditure, and urinary catecholamine excretion were determined three times for eight hours each during each shift work day. The following results were obtained: 1) No significant changes were detected in the physiological parameters before and after each shift work, except for elevation in plasma adrenaline level after night shift. 2) Heart rate, blood pressure and subjective fatigue rating tended to be higher, though not significantly, at the beginning of night shift, when compared with the data obtained on the some time of day, i.e., at the end of evening shift. 3) On the other hand, the plasma cortisol level tended to be suppressed after night shift, suggesting that even one night shift work may change the circadian rhythm of plasma cortisol. 4) Statistical analyses showed that in contrast to day and evening shift, in night shift there was no significant positive correlation between eight-hour walk steps, and eight-hour mean heart rate and urinary adrenaline excretion, suggesting an altered circadian rhythm in heart rate and urinary adrenaline excretion and also a possible additional psychological load in night shift. These results suggest that even one night shift work could modulate the autonomic nervous-adrenal activity of hospital nurses, compared with day or evening shift, and indicate that it is necessary to lengthen the time interval before and after night shift work.