2013 年 7 巻 3-4 号 p. 35-43
The aim of this study was to investigate the effects of a rotating-shift schedule on nurses' vigilance by comparing vigilance before and after day-shift duties and night-shift duties. We conducted objective and subjective sleep and vigilance tests by means of actigraphy and the Psychomotor Vigilance Task, and we attempted to identify common factors in the sleep habits of participants with conspicuously low vigilance. A total of 13 rotating-shift female nurses, aged 25-62 years, participated in the one-week study. Means of reaction time (RT) were adjusted to 1/RT to account for the possibility of outliers. A significant decrease of vigilance was detected after night-shift duty (mean 1/RT of 0.0033 ± 0.0008 ms before duty vs. 0.0031 ± 0.0008 ms after duty, F [1,2] = 224.64, p < 0.01). A significant individual difference in vigilance was observed for day shifts (F [12,19] = 5.49, p < 0.01). We also found that a wider spread of day-by-day total sleep time (TST) was associated with a longer mean RT (r =0.64, p = 0.02), while no clear correlation between the mean TST and RT was found. Our findings suggest that rotating-shift work may have a negative impact on vigilance during night shifts, while an irregular duration of sleep during the week may reduce vigilance during day shifts. Our results further suggest that the negative effects of rotating shifts occur not only during night shifts but also during day shifts if sleep length varies day by day.