2015 Volume 91 Issue 5-6 Pages 62-71
We investigated the relationship between three different timings of nap and concentration of urinary 6-sulphatoximelatonin (aMT6s) for 134 nurses (125 women and 9 men; 34.5±9.3 years old±SD) assigned to double 8-hour night shifts. Three nurses worked for each night shift and took their naps of around 2 hours in succession, with the first nap (23：15-01：22), the second nap (01：20-03：23) and the third nap (03：26-05：21). The urinary aMT6s collected during the nighttime sleep after a day shift (control condition) and during the nap at night shift (experimental condition) were analyzed by Dr. Minami's procedure (2009). The results showed that levels of urinary aMT6s during the nighttime sleep after a day shift were significantly higher than during the nap in the night shifts (p=0.007). However, there were no significant differences in levels of aMT6s in terms of the nap timings and interactions. Furthermore, no significant differences were obtained, even if analyzed by the duration of nap periods and the start time of naps, respectively. Therefore, we conclude that whenever hospital nurses have taken a nap during double 8-hour night shifts, urinary aMT6s will be at similar levels and also fall short of the levels during a nighttime sleep after a day shift.