Abstract
BackgroundThe aim of the present study was to assess the risk of having a traffic accident after using alcohol, single drugs, or a combination, and to determine the concentrations at which this risk is significantly increased.MethodsA population-based case-control study was carried out, collecting whole blood samples of both cases and controls, in which a number of drugs were detected. The risk of having an accident when under the influence of drugs was estimated using logistic regression adjusting for gender, age and time period of accident (cases)/sampling (controls). The main outcome measures were odds ratio (OR) for accident risk associated with single and multiple drug use. In total, 337 cases (negative: 176; positive: 161) and 2726 controls (negative: 2425; positive: 301) were included in the study.ResultsMain findings were that 1) alcohol in general (all the concentrations together) caused an elevated crash risk; 2) cannabis in general also caused an increase in accident risk; at a cut-off of 2 ng/mL THC the risk of having an accident was four times the risk associated with the lowest THC concentrations; 3) when ranking the adjusted OR from lowest to highest risk, alcohol alone or in combination with other drugs was related to a very elevated crash risk, with the highest risk for stimulants combined with sedatives.ConclusionThe study demonstrated a concentration-dependent crash risk for THC positive drivers. Alcohol and alcohol-drug combinations are by far the most prevalent substances in drivers and subsequently pose the largest risk in traffic, both in terms of risk and scope.
Highlights
Alcohol and cannabis are amongst the substances most widely used by drivers in Europe [1,2,3]
Legitimate concern exists about the influence of alcohol and other drugs on traffic safety
The patient form included the minimum required data, i.e.: Maximum Abbreviated Injury Scale (MAIS); identification number; hospital; date and time of the accident; vehicle type; drugs and fluids administered in hospital before sampling; age and gender of patient; time between accident and sampling; single or multiple vehicle accident
Summary
Alcohol and cannabis are amongst the substances most widely used by drivers in Europe [1,2,3]. A recent roadside study in 13 European countries revealed that alcohol was the most prevalent (3.48%) among drivers, followed by illicit drugs (1.9%, with cannabis most frequently detected), and medicinal drugs (1.36%) [1]. By means of epidemiological studies, the risk of having an accident (risk assessment; case-control studies) and the risk of being responsible for a crash (responsibility or culpability estimates; called case-crossover studies) can be calculated. Both are valid methods to study and understand the impact of drug use on traffic safety. The aim of the present study was to assess the risk of having a traffic accident after using alcohol, single drugs, or a combination, and to determine the concentrations at which this risk is significantly increased
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