Investigating the Association Between Sedative Hypnotic Prescription Exposures and Motor Vehicle Crashes

Thesis (Ph.D.)--University of Washington, 2012Background Motor vehicle crashes occur daily and may be fatal for the driver, passengers or bystanders. Crashes have been shown to be associated with certain medical conditions and exposure to prescription medications that impair the ability to drive. We sought to create a linked, population-based longitudinal crash and medical care use dataset and to evaluate the relationships between prescription opioid and sedative hypnotic medication exposures and automobile crashes in Washington State. Methods Crash data from the Washington State Department of Transportation from 2002 to 2009 were linked to medical, pharmacy and administrative data from the Group Health Cooperative (GHC) for all eligible members. Continuous prescription exposures were defined based on fill records for opioids and sedatives. We estimated multivariate extended Cox regressions to investigate the association between police-reported crashes and prescription fills for opioids and sedative hypnotics. We also stratified our analyses by the length of continuous prescription fills. Results A total of 676,694 subjects were included in the study. These individuals experienced 2.41 motor vehicle crashes per 100 person-years. Opioid prescription fills were associated with a hazard ratio of 1.37 (95% CI: 1.33 to 1.41). Stratifying opioid exposure by the length of continuous prescriptions resulted in a range of hazard ratios from 1.76 at 30 days (95% CI: 1.59 to 1.96) up to 11.33 at 120 days (95% CI: 9.18 to 13.98). Overall incident sedative prescriptions were associated with a hazard ratio of 2.23 (95% CI: 1.92 to 2.59). Stratifying continuous prescriptions by length revealed the highest risk group to be 121-240 days for all sedatives, trazodone and temazepam (overall HR: 6.84, 95% CI: 4.15 to 11.2). Zolpidem had no risk of crash in the first 30 days, yet risk climbed to a peak risk between 241-360 days (HR: 10.7, 95% CI: 3.9 to 29). Discussion The risk of motor vehicle crash is increased in people who fill prescriptions for opioids and sedative hypnotics. The hazard ratios estimated are equivalent to blood alcohol concentrations in excess of double the legal limit to drive. Public health may be improved by reducing driving time when using these medications