In a simulation study evaluating the residual effects of taking a single night-time dose of hypnotics among health individuals on collision anticipation capacities in the next morning, investigators found no residual effect by having taken a capsule of zolpidem. In a real world, however, zolpidem is frequently consumed not only by sleep disorder patients without any other comorbidities, but also patients with multiple chronic diseases. A post-marketing study of zolpidem revealed the incidence of the residual daytime sedation being 3.7%, which was reported to be unlikely based on various experimental circumstances with selected participants demonstrating negligible impairments. In fact, several studies with real world settings have reported positive relationship between the zolpidem and the traffic accident. while evidence among Asian population is scant. 

Recent analysis of national health insurance data of Taiwan showed use of zolpidem at night of the previous day might be associated with an increased risk of motor vehicle collision (MVC) related hospitalization. The study used 1 million patient sample data of whole Taiwan population to identified hospitalized drivers with MVCs and prescription record of the zolpidem before the hospitalization. However, the inclusion of MVC leading to only hospitalization might have led to underrepresentation of fatal cases that had no admission record. Moreover, the study was limited by lack of control for important confounders, because no information on detailed context of MVCs or alcohol consumptions was available. We aimed to evaluate the risk of fatal MVCs by use of zolpidem considering the context of the MVCs.