New opioid analgesic use and the risk of injurious single-vehicle crashes in drivers aged 50-80 years: A population-based matched case-control study

Background: the increasing trend in opioid analgesic use among older drivers has raised concerns about their risk of being involved in car crashes. Aim: to investigate if older drivers who started using opioid analgesics have a higher probability of being involved in injurious crashes. Methods: population-based matched case-control study. Data from population registers were merged using a personal identity number. Cases were drivers aged 50-80 years responsible for a single vehicle crash between 01.07.05 and 31.12.09 that led to at least one injured passenger (n = 4,445). Four controls were randomly matched to each case by sex, birth month/year, and residence area from persons holding a valid driving license who did not crash during the study period. New use was defined as at least one dispensation within 1-30 days prior to the crash, but none within the previous 31-180 days; frequent use when >= 3 dispensations were given within 0-180 days, with at least one within 31-180 days. Individuals using 1-2 non-opioid analgesic medications were used as reference category. Conditional logistic regression was used to estimate odds ratios (OR; 95% CI) adjusting for benzodiazepine use, co-morbidity, civil status and occupation. Results: adjusted odds for new use were two-fold that of drivers using 1-2 non-opioid analgesics medications (2.0; 1.6-2.5). For frequent use, adjusted odds were also increased regardless of number of dispensations (3-4 = 1.7; 1.3-2.1, 5-6 = 1.6; 1.2-2.3, and >= 7 = 1.7; 1.3-2.1). Conclusion: new, but also frequent opioid analgesic use, resulted in an increased probability of single vehicle crashes. While more epidemiologic evidence is needed, patients could be advised to refrain from driving when using opioid analgesics.