The Prevalence of Substance Use in Injured Off-Road Vehicle Drivers: A Systematic Review and Observational Study

Abstract

Background: Drug driving has become as common as alcohol-impaired driving in Canada and is a major public health issue. Substance use in the context of off-road vehicle driving (i.e., ATVs, snowmobiles, dirt bikes) has not been well-studied in Canada. The prevalence of acute substance use in injured off-road vehicle drivers across Canada is currently unknown. The aim of this study is to estimate the prevalence of acute substance use among injured off-road vehicle drivers in Canada.

Objectives: This thesis includes two main studies and three key objectives.

Part 1: Systematic Review and meta-analysis The first study involves a systematic review and meta-analysis, with the purpose of (1) estimating the prevalence of acute substance use in drivers involved in off-road vehicle crashes.

Part 2: Observational Study The second study is a primary study of injured off-road vehicle drivers presenting to emergency departments across Canada. The two objectives of this study are: (2) to estimate the prevalence of acute substance use in injured off-road vehicle drivers presenting to emergency departments in Canada; and (3) to determine what factors (i.e. demographic, crash characteristics, regional variation) are associated with acute substance use in injured off road vehicle drivers presenting to emergency departments in Canada.

Systematic Review Methods: Studies were identified from electronic databases and grey literature. Study selection, data extraction, and risk of bias assessment were completed by two independent reviewers. Descriptive statistics were used to report study characteristics. Random effects meta-analyses were used to report the overall pooled prevalence, and subgroup and sensitivity analyses were used to explore study characteristic effects and the robustness of results.

Primary Study Methods: Employing data from the National Drug Driving Study, this study analyzed data from injured drivers presenting to 18 participating EDs across Canada who were in an off-road vehicle crash and had blood drawn for clinical purposes. Excess blood from clinical use underwent toxicology analysis to quantify the presence of impairing substances in the injured driver. Prevalence estimates of substance use in injured off-road vehicle drivers were reported overall, by substance type, by level of alcohol and tetrahydrocannabinol (THC), by number of substances and disaggregated by relevant covariates.

Results: 20 publications comprising of 18 studies were included for review, with 2 sets of publications that had overlapping data, drawn from the same studies. Prevalence estimates ranged from 8% to 85%. The overall pooled prevalence estimate of substance use was 41% (95% CI: 28%-54%). There was significant heterogeneity across studies (Q = 3456.38, p < 0.001; I2=99.4%). Subgroup analyses found significant differences between studies using different data sources (coroner’s data: 57% (43%-71%) vs. hospital data (29% (6%-58%), and between non-fatally (29%, 95% CI: 9%-55%) and fatally injured drivers (56%, 95% CI: 43%-69%).

The observational study included 473 injured drivers who met the inclusion criteria. Overall, 71% of tested drivers were positive for at least one impairing substance. Alcohol was detected in 38% of drivers, and 69% of those drivers were above the legal blood alcohol concentration (BAC) limit of 0.08% BAC. THC was detected in 17% of drivers. Central nervous system (CNS) depressants were detected in 31%, opioids in 14%, and CNS stimulants in 13% of drivers. About a third (32%) of drivers tested positive for more than one substance.

Conclusion: These findings reveal that a large proportion of injured off-road vehicle drivers test positive for substances, which indicates a serious public health issue. Targeted interventions for at-risk populations and increased law enforcement are required to reduce impaired driving among off-road vehicle drivers.