Innovative working schedule: introducing one short nap during the night shift

In order to test the possible long-term effects of the implementation of a short nap during night shifts, an experiment was conducted over a period of 1 year with 12 volunteer shiftworkers operating in an industrial plant. Th ey were authorized, under certain conditions, to use individual sleeping ar eas, for a maximum of 1 hour, between 23h30 and 3h30. The participants were asked to fill in a short questionnaire every day during the entire study. The questions concerned the schedule of the main sleep period, the afternoo n nap and the night-time nap, if any, as well as the evaluation of mood and the quality of work. This daily questionnaire was supplemented by an exten sive questionnaire applied every 2 months in order to assess the main chang es introduced in the life of the participants by this new working schedule. Results showed that this new organization introduced a general satisfactio n about the quality and the easiness of the work at night. The vigilance le vel was considered to be higher during the hours following the nap. The eff icacy of the nap time progressively increased for most subjects. The genera l quality of life improved for most subjects. While a few of them considere d that falling asleep was less easy on the following morning at home, the s tatistical analysis did not show any detrimental effect of the short rest p eriod on the length of the immediately consecutive main sleep period. Howev er, different statistical analyses allow us to reveal significant differenc es between the main sleep durations following the night shift compared with those following both the afternoon shift and the resting period. The main sleep duration following the night shift was not statistically different fr om that of the morning shift. These results are very encouraging. A short n ap during the night shift can be considered as a positive way to counteract the low level of vigilance that normally occurs during the late part of th e night.