[How Japanese hospital nurses take naps between a day shift and a night shift when they work the two shifts consecutively].

The purpose of our study is to make clear when, where and how long Japanese hospital nurses take naps before night work (pre-work nap) when they work a day shift and a night shift consecutively. The day shift ends at 16:45 and the night shift starts at 00:00. To examine the effect of the pre-work nap on tiredness after night work (post-work tiredness) is another purpose. In our study, we analyzed the results of a questionnaire survey of 2,001 hospital nurses working under an irregular three shift system. The results of our study showed that mean nap duration for all the nurses was 163.0 min. As the nurses' age increased, the percentage of nurses taking the pre-work naps decreased and mean nap duration also shortened. It was also found that the percentage for nurses with small children aged 0-5 years was very low and their mean nap duration was much shorter than that of unmarried nurses or married nurses without children. It was revealed that 28.7% of the all nurses took the pre-work nap in the hospital and the mean duration of napping in the hospital was much longer than that of napping at home. The mean nap starting time was 19:37 and the later the nap starting time was the shorter the mean nap duration was. As to the effect of the pre-work nap, when the nap duration was longer, sleepiness tended to occur later during night work. Pre-work napping for more than 180 min significantly lowered the mean score for post-work tiredness, compared to no napping, but a nap taken during night work (mid-work nap) was more effective than the pre-work nap for lowering the mean score for post-work tiredness.