Background and Goal of Study: Drowsiness is an increasing national health problem in France. It was responsible for many crashes in towns and the first cause of death on highways in 2009 . Medical staff is at risk to drive in a drowsy state when returning at home after a working night shift duty. We conducted an experimental study in a simulated driving laboratory to evaluate the consequences of sleep deprivation on driving performance of anaesthesia trainees after a working night shift duty.
Materials and Methods: Thirty residents were investigated after a shift of night duty (sleep deprived condition [SDC]) and after a night of normal sleep (control condition [CC]) in a comparative cross-over study. The order of sessions was randomized for each resident. Aptitude was tested in a simulated driving laboratory (INRETS-FAROS) where participants drove 15 minutes in town (urban conditions) followed by 60 minutes on a highway (monotonous conditions). Endpoints were the reaction time, the mean speed and the numbers of crashes in urban conditions and the standard deviation of lateral position (SDLP) and the standard deviation of speed (SDS) in monotonous conditions.
Results and Discussion: In urban conditions, residents tended to drive faster in CC than in SDC (43 km/h vs. 41 km/h, p=0,08). No significant difference was found between groups in the reaction time and the number of crashes. In monotonous conditions, SDLP and SDS were significantly higher in SDC than in CC (SDLP: F(1,27) = -2,19; p = 0,02) and SDS: F(1,27) = -2,25; p = 0,03). This difference appeared after 20 and 30 minutes driving, respectively, and continued until the end of the test.
Conclusion(s): The results showed the residents' performances decreased after a shift of night duty under monotonous conditions. They experienced more lateral deviation and had some difficulty to control their speed. Under urban conditions, residents in SDC seemed to use a preventive strategy by decreasing their speed. Our study confirms that it is dangerous to drive in monotonous conditions after a night shift duty. Further studies are mandatory to validate the simulation model for urban driving conditions.
1. Observatoire national interministériel de sécurité routière. La sécurité routière en france, bilan de l'année 2009. La documentation Française 2010. Synthèse générale:8-34.