Psychoactive substance use and the risk of motor vehicle accidents

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Abstract

The driving performance is easily impaired as a consequence of the use of alcohol and/or licit and illicit drugs. However, the role of drugs other than alcohol in motor vehicle accidents has not been well established. The objective of this study was to estimate the association between psychoactive drug use and motor vehicle accidents requiring hospitalisation.

A prospective observational case-control study was conducted in the Tilburg region of The Netherlands from May 2000 to August 2001. Cases were car or van drivers involved in road crashes needing hospitalisation. Demographic and trauma related data was collected from hospital and ambulance records. Urine and/or blood samples were collected on admission.

Controls were drivers recruited at random while driving on public roads. Sampling was conducted by researchers, in close collaboration with the Tilburg police, covering different days of the week and times of the day. Respondents were interviewed and asked for a urine sample. If no urine sample could be collected, a blood sample was requested.

All blood and urine samples were tested for alcohol and a number of licit and illicit drugs. The main outcome measures were odds ratios (OR) for injury crash associated with single or multiple use of several drugs by drivers.

The risk for road trauma was increased for single use of benzodiazepines (adjusted OR 5.1 (95% Cl: 1.8–14.0)) and alcohol (blood alcohol concentrations of 0.50–0.79 g/l, adjusted OR 5.5 (95% Cl: 1.3–23.2) and ≥0.8 g/l, adjusted OR 15.5 (95% Cl: 7.1–33.9)). High relative risks were estimated for drivers using combinations of drugs (adjusted OR 6.1 (95% Cl: 2.6–14.1)) and those using a combination of drugs and alcohol (OR 112.2 (95% Cl: 14.1–892)). Increased risks, although not statistically significantly, were assessed for drivers using amphetamines, cocaine, or opiates. No increased risk for road trauma was found for drivers exposed to cannabis.

The study concludes that drug use, especially alcohol, benzodiazepines and multiple drug use and drug–alcohol combinations, among vehicle drivers increases the risk for a road trauma accident requiring hospitalisation.

Introduction

The Grand Rapids Study convincingly showed that driving under influence of alcohol is an important risk factor for traffic accidents (Borkenstein et al., 1974). The role of drugs other than alcohol in motor vehicle accidents, however, has not been well established. Many medicines (prescription or over-the-counter) and illicit drugs affect the nervous system (Ramaekers, 1998). Driving under the influence of drugs other than alcohol is considered to be an increasing cause of traffic accidents worldwide (Morland, 2000).

Several classes of drugs, including amphetamines, antihistamines, cannabis, hypnotics, tranquillizers and tricyclic antidepressants, have been shown to impair driving skills in laboratory tests and driver-simulation studies (O’Hanlon and Volkerts, 1986, Smiley, 1987, Robbe, 1998). These studies are restricted in various ways, e.g. with regard to subject selection and divergent behaviour or sample size. Their generalization to a ‘real’ traffic situation is debated. Many observational studies have shown that drug use as determined by biological sampling among drivers is prevalent and increasing (Gjerde et al., 1993, Soderstrom et al., 1997, Morland, 2000). Several studies tried to provide accident risk estimates related to drug use by linking drug prescription records to hospital admission records involving motor vehicle accidents, police reports, or health insurance records (Skegg et al., 1979, Ray et al., 1992, Leveille et al., 1994, Neutel, 1995, Hemmelgarn et al., 1997, Barbone et al., 1998, McGwin et al., 2000). In addition, a few studies have been conducted in which non-trauma patients were included as controls (Honkanen et al., 1980, Marquet et al., 1998). These studies provided risk estimates, but a limitation is that the control groups were not taken from moving traffic.

The objective of our study was to estimate the association between the use of various psychoactive substances and serious traffic injuries needing hospitalisation by comparing exposure frequencies (prevalences) of these substances in injured and non-accident involved drivers.

Section snippets

Setting

The study was conducted in co-operation with a large general teaching hospital (St. Elisabeth Hospital) and the police department located in the Dutch city of Tilburg, covering a population of approximately 350,000 persons. The hospital has all the facilities comparable with a highly equipped trauma centre. The source populations of our study were injured and non-accident involved drivers throughout the period from May 2000 until August 2001. The hospital’s Medical Ethics Committee approved the

Results

We were able to identify and include 110 injured motorists. The relatives of two deceased patients refused consent and their data were excluded from analysis. The mean ISS for the case patients was 14 (range 1–75) of the 1029 controls, 816 (79.3%) drivers complied to participate. In the case group 39% of the specimens consisted out of urine compared to 85% in the controls, respectively. Overall, 74% of the study subjects were men. The mean age was 38.6 years. Control subjects were older than

Discussion

This study indicates that use of alcohol, amphetamines, benzodiazepines, cocaine, and opiates places drivers at increased risk for motor vehicle accidents requiring hospitalisation. Users of drug–drug combinations were at a sixfold increased risk. Vehicle drivers who were exposed to drug–alcohol combinations were at the highest risk of experiencing injurious road accidents.

The prevalence for drug and alcohol found in this study is consistent with literature on impaired drivers, or drivers

Conclusions

In conclusion, although a causal relationship between road trauma accidents and the use of drugs other than alcohol is not proven by the results of this study, it provides new insights in the role of these drugs in traffic crashes. Use of drug–drug combinations constitute a risk for drivers that will be at least as severe as the risk caused by the use of moderate quantities of alcohol. The impact on society is significant and actions related to reducing the use of these drugs by drivers are

Acknowledgements

The authors are indebted to R. Langen and F. van Hoof for their critical comments regarding the laboratory drug analysis. We acknowledge The Netherlands Forensic Institute, the Dutch Laboratory for Drugs Doping and the SWOV Institute for Road Safety Research for their co-operation in this study.

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    Present address: Department of Clinical Pharmacy, Medical Spectrum Twente Hospital group, Enschede, The Netherlands.

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