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

Although various prescription drugs may be equally effective in promoting sleep, some may lead to substantial impairment in psychomotor functioning and an increased risk of motor vehicle accidents. 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. Impairment in driving performance, as evaluated by randomised controlled open-road studies using the standard deviation of a vehicle's lateral position (SDLP), a measure of weaving, was expressed in terms of equivalent blood alcohol (ethanol) concentration (BAC). Epidemiological data were then used to relate BAC to the excess risk of motor vehicle accidents. Although a non-impairing medication would not increase risk, a medication that produces mild impairment in driving performance (a change of 2.5 cm in SDLP, equivalent to 0.05% BAC) would increase motor vehicle accident risk by 25%. One that leads to moderate impairment (an SDLP change of 4.5 cm, equivalent to 0.08% BAC) would roughly double this risk, and a severely impairing medication (an SDLP change of 7 cm, equivalent to 0.12% BAC) would result in up to a 5-fold increase in motor vehicle accident risk. For application to the French setting, a hypothetical cohort of 100,000 adult drivers with insomnia was assumed to be treated for 14 days either with zaleplon 10 mg, a new sleep medication that has been shown not to significantly impair driving performance, or zopiclone 7.5 mg, which has been shown to cause moderate impairment. Compared with zaleplon, use of zopiclone over 14 days in France would 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 values). Our model illustrates the extent to which non-impairing sleep medications could reduce the burden posed by motor vehicle accidents. Our model is designed to be general, and thus can serve as the basis for similar investigations.