Prescription of Zolpidem and the Risk of Fatal Motor Vehicle Collisions: A Population-Based, Case-Crossover Study from South Korea.

BACKGROUND: Zolpidem is one of the most frequently used hypnotics worldwide, but associations with serious adverse effects such as motor vehicle collisions have been reported. OBJECTIVE: The objective of this study was to evaluate the association of fatal motor vehicle collisions with a prescription for zolpidem, considering the context of the motor vehicle collisions. METHODS: We conducted a case-crossover study, where each case served as its own control, by linking data about fatal motor vehicle collisions from the Korean Road Traffic Authority between 2010 and 2014 with national health insurance data. The case period was defined as 1 day before the fatal motor vehicle collisions, and was matched to four control periods at 90-day intervals. Conditional logistic regression was performed to calculate the odds ratio for fatal motor vehicle collisions associated with zolpidem exposure, and odds ratios were adjusted for time-varying exposure to confounding medications. A stratified analysis was performed by age group (younger than 65 years or not), the Charlson Comorbidity Index, and whether patients were new zolpidem users. RESULTS: Among the 714 subjects, the adjusted odds ratio for a fatal motor vehicle collision associated with a prescription for zolpidem the previous day was 1.48 (95% confidence interval 1.06-2.07). After stratification, a significantly increased risk was observed in subjects with a high Charlson Comorbidity Index (odds ratio 1.81; 95% confidence interval 1.16-2.84), the younger age group (odds ratio: 1.62; 95% confidence interval 1.03-2.56), and new zolpidem users (odds ratio 2.37; 95% confidence interval 1.40-4.00). CONCLUSION: A prescription for zolpidem on the previous day was significantly related to an increased risk of fatal motor vehicle collisions in this population-based case-crossover study.