A general model of the effects of sleep medications on the risk and cost of motor vehicle accidents and its application to France

Background: Although various prescription drugs may be equally effective in promoting sleep, some may lead to substantial impairment in psychomotor fu nctioning and an increased risk of motor vehicle accidents. Objective: To develop a general model to evaluate the potential effects of sleep medications on motor vehicle accidents and costs, and apply the model to the French setting. Methods: Impairment in driving performance, as evaluated by randomised cont rolled open-road studies using the standard deviation of a vehicle's latera l position (SDLP), a measure of weaving, was expressed in terms of equivale nt blood alcohol (ethanol) concentration (BAC). Epidemiological data were t hen used to relate BAC to the excess risk of motor vehicle accidents. Altho ugh a non-impairing medication would not increase risk, a medication that p roduces mild impairment in driving performance (a change of 2.5cm in SDLP, equivalent to 0.05% BAG) would increase motor vehicle accident risk by 25%. One that leads to moderate impairment (an SDLP change of 4.5cm, equivalent to 0.08% BAG) would roughly double this risk, and a severely impairing med ication (an SDLP change of 7cm, equivalent to 0.12% BAG) would result in up to a 5-fold increase in motor vehicle accident risk. For application to th e French setting, a hypothetical cohort of 100 000 adult drivers with insom nia was assumed to be treated for 14 days either with zaleplon 10mg, a new sleep medication that has been shown not to significantly impair driving pe rformance, or zopiclone 7.5mg, which has been shown to cause moderate impai rment. Results: Compared with zaleplon, use of zopiclone over 14 days in France wo uld be expected to result in 503 excess accidents per 100 000 drivers at an additional cost of 158 French francs (31 US dollars) per person (1996 valu es). Conclusions: Our model illustrates the extent to which non-impairing sleep medications could reduce the burden posed by motor vehicle accidents. Our m odel is designed to be general, and thus can serve as the basis for similar investigations.