Residual effects of hypnotic drugs in aging drivers submitted to simulated accident scenarios: an exploratory study

The effects of hypnotic drugs on driving performance are most often evaluated on young healthy subjects by using a monotonous motorway driving test. The effects of drugs in urban driving situations have not yet been evaluated in any age group. Our objectives were to assess residual effects of the most prescribed hypnotics, zolpidem and zopiclone, on older middle-age drivers' capacities in an urban situation. Sixteen healthy subjects aged 55 to 65 years underwent this double-blind, balanced, cross-over study. Zopiclone (7.5 mg), zolpidem (10 mg), and flunitrazepam (1 mg; used as positive control) or a placebo were administered at each subject's home at 11:00 pm under the supervision of an investigator. The next morning, the subjects had to drive in a simulated urban environment where accident scenarios were introduced. Accident scenarios were implemented using data from real accident cases. Hypnotics did not significantly increase the number of collisions. However, significantly higher speeds were found with zopiclone and flunitrazepam; moreover, zolpidem and zopiclone induced modifications of the lateral position of the car on the road. This study did not reveal any major residual effects of the hypnotics studied on driving performance in aging drivers. However, the urban driving situations used here for the first time in the evaluation of drugs revealed some modifications in driving habits which could lead to risky behavior. It thus appears that urban driving simulations are useful for gaining knowledge about the effects of drugs on driving behavior.