2013 Volume 89 Issue 6 Pages 218-224
In recent years, the systems of working shifts for nurses in Japanese hospitals have rapidly changed from conventional three-shift systems to two-shift systems. This change has been accompanied with a marked increase in the number of 16-hour night shifts, which consist of the evening and night shifts worked in succession. This study investigated the subjective sleepiness in nurses working such long night shifts.
At hospitals where a 16-hour night shift had been introduced, three nurses per ward worked the night shift. Data were collected from a total of 145 nurses working in 9 wards of 8 hospitals for 5 days from Monday to Friday. Workloads were determined by means of actograms and subjectively assessed busyness ratings recorded every 10 minutes time in a budget study. Sleepiness was also evaluated by the time budget study. The mean age of the nurses was 33.6 years (standard deviation 8.9). The actual on-duty hours per night shift including elective overtime amounted to 18.3 hours (standard deviation 0.8). On average, nurses started the shift at 15：34 (standard deviation 33 min) and finished at 9：41 (standard deviation 33 min). Three nurses took a nap at different times during the night shift, starting around 23：00 (the first nap), 1：00 (the second nap), and 3：00 (the third nap).
Actograms and busyness ratings (r=0.907, p<0.001) followed a bimodal course during the night shift, with two peaks at around 18：00 and 7：00. The highest sleepiness was reported at 5： 20 (26.8%), followed by 9：10, 3：10, 0：20 and 0：30. The sleepiness (t =19.65, p<0.001) and busyness ratings (t =24.279, p<0.001) during the night shifts were higher than those during the evening shift. The third nappers had the highest sleepiness than other nappers during working hours until the nap time (p<0.001) and during early morning hours after the nap period (p=0.041).
We conclude that a 16-hour night shift may have certain benefits in maintaining the circadian rhythm for daytime work, since the night shift occurs only once in 5 days and nurses can take a nap during the night shift. However, it also resulted in frequent sleepiness, particularly, in the case of the third nappers, during such a long night shift.