The Journal of Science of Labour
Online ISSN : 2187-2570
Print ISSN : 0022-443X
Short Communications
Prevalence of the Subjective Sleepiness in Nurses Working 16-hour Night Shifts
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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 [12]=19.65, p<0.001) and busyness ratings (t [12]=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.

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© 2013 The Institute for Science of Labour
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