Alcohol and Illicit Drugs and the risk of Injurious Road Traffic Crashes in High-Income Countries: A Systematic Review

Problem

Despite legislation to reduce substance-related road traffic crashes (RTCs), their incidence continues to be a worldwide public health problem. The healthcare burden from RTCs is often seen in primary care through long-term management of injury sequela and supporting adults’ return to work. To date, a systematic review has not been conducted to explore the magnitude of alcohol and illicit drug use among drivers involved in RTCs in high-income countries. This study aimed to investigate the association between alcohol- and drug-intoxicated drivers, and the risk of sustaining an injurious RTC compared to abstinent drivers in high-income countries. Furthermore, this study aimed to determine whether the severity of injury is dependent on the exposure type.

Approach

A systematic review was conducted. Comprehensive searches were conducted using 4 electronic databases (MEDLINE, EMBASE, TRID, WHOLIS) in April 2017 to identified comparative observational studies assessing the effect of exposure to alcohol and/or illicit drugs on the risk of injurious RTC. We excluded studies which investigated law enforcement measures or those which were legislative. Reference lists of identified studies and reviews were also screened to identify further studies. No language restrictions were imposed during the searching. Titles and abstract, and full text screening was performed independently by two authors, with discrepancies resolved through discussion. Included studies were comparative observational studies of licensed drivers that had sustained road traffic injury. Where possible, data were pooled using random effects meta-analyses. Heterogeneity was quantified using I2. Subgroup analyses were conducted to investigate heterogeneity. Publication bias was assessed visually using funnel plots.

Findings

27 studies were eligible to be included in the review. 15 studies investigated alcohol alone as the exposure; 11 studies examined both drugs and alcohol, and the remaining study investigate drugs alone. The risk of injury was increased in drivers under the influence of alcohol (OR 16.00, 95% CI 7.59-33.71, I2=97%, 11 studies), any drug (OR 2.61, 95% CI 1.17-5.84, I2=92%, 6 studies), marijuana (OR 1.84, 95% CI 2.43-31.98, I2=0%, 6 studies), amphetamines (OR 1.84, 95% CI 1.50-2.27, I2=79%, 3 studies) and alcohol and drugs combined (OR 62.31, 95% CI 27.71-140.09, I2=79%, 5 studies). Drivers influenced by alcohol were also found to significantly increase their risk of fatal injury compared to non-fatal injury. No evidence of publication bias was detected.

Consequences

Drivers under the influence of certain substances have an increased likelihood of sustaining road traffic injuries. Greater enforcement measures, combined with opportunistic alcohol brief advice in primary and secondary care are recommended to reduce substance-influenced drivers. Better quality studies are required to fully determine the impacts of drugs on driving.