Alcohol- or drug-use disorders and motor vehicle accident mortality: a retrospective cohort study

A large body of research has linked alcohol consumption and motor vehicle accidents (MVAs), but far fewer studies have estimated the risk of MVA fatality among drug users. Our study addresses this gap. We identified cohorts of individuals hospitalized in California from 1990 to 2005 with ICD-9 diagnoses of methamphetamine- (n=74,170), alcohol- (n=592,406), opioids- (n=68,066), cannabis- (n=47,048), cocaine- (n=48,949), or polydrug-related disorders (n=411,175), and these groups were followed for up to 16 years. Age-, sex-, and race-adjusted standardized mortality rates (SMRs) for deaths due to MVAs were generated in relation to the California general population. Standardized MVA mortality ratios were elevated across all drug cohorts: alcohol (4.5, 95% CI, 4.1-4.9), cocaine (3.8, 95% CI, 2.3-5.3), opioids (2.8, 95% CI, 2.1-3.5), methamphetamine (2.6, 95% CI, 2-3.1), cannabis (2.3, 95% CI, 1.5-3.2) and polydrug (2.6, 95% CI, 2.4-2.9). Males and females had similar MVA SMRs. Our large, population-based study found elevated risk of MVA mortality across all cohorts of individuals with alcohol- or drug-use disorders. Given that illicit drug users are often unaware of or misperceive the impacts of drug use on safe driving, it may be important for health-service or public-health interventions to address such biases and improve road safety.