Comparison of the prevalence of alcohol, cannabis and other drugs between 900 injured drivers and 900 control subjects: results of a French collaborative study

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Abstract

A collaborative case-control study was conducted in France in order to determine the prevalence of alcohol, cannabinoids, opiates, cocaine metabolites, amphetamines and therapeutic psychoactive drugs in blood samples from drivers injured in road accidents and to compare these values with those of a control population. Recruitment was performed in emergency departments of six university or general hospitals and comprised 900 drivers involved in a non-fatal accident and 900 patients (controls) who attended the same emergency units for a non-traumatic reason. Drivers and controls were matched by sex and age. Alcohol was determined by flame ionization–gas chromatography, drugs of abuse (DOA) by gas chromatography–mass spectrometry with the same analytical procedures in the six laboratories, and medicines by high performance liquid chromatography with diode array detection.

Blood alcohol concentration exceeding 0.5 g/l (i.e. the legal French threshold) was found in 26% of drivers and 9% of controls. In the 18–27 years age range, alcohol was the only toxic found in blood samples of 17% drivers and 5% controls, leading to an odds-ratio (OR) of 3.8. A significant relationship was found between alcohol blood concentrations and OR values. All age groups confounded, the main active substance of cannabis, Δ9 tetrahydrocannabinol (THC), was found in 10% of drivers and 5% of controls. In the less than 27 years old, THC (>1 ng/ml) was detected alone in the blood of 15.3% drivers and of 6.7% controls, giving OR=2.5, whereas there was no link between THC blood concentrations and OR value. THC was found alone in 60% of cases and associated with alcohol in 32%, with OR=4.6 between drivers and controls for this association. The difference in morphine prevalence between drivers (2.7%) and controls (0.03%) was highly significant (P<0.001), with OR=8.2. The number of positive cases for amphetamines and cocaine metabolites was too low for reaching any interpretation. The most frequently observed psychoactive therapeutic drugs were by far benzodiazepines, that were found alone in 9.4% of drivers and 5.8% of controls, which led to OR=1.7 (P<0.01).

This study demonstrates a higher prevalence of opiates, alcohol, cannabinoids and the combination of these last two compounds in blood samples from drivers involved in road accidents than in those from controls, which suggests a causal role for these compounds in road crashes.

Introduction

Most drugs that affect the central nervous system may have the potential to impair driving ability. Alcohol, drugs of abuse (DOA: opiates, amphetamines, cocaine and cannabis) and prescribed psychoactive drugs are potentially concerned. For many years, attention has primarily focused on alcohol and most countries have established legal limits for blood alcohol concentration during driving. However, during the last years drugs other than alcohol have attracted increasing attention, due to a dramatic increase of use, particularly for cannabis which is by far the most consumed DOA in France as well as in many other countries. Research on the impairing effects of these psychoactive compounds has included several approaches [1]. Some studies have evaluated the effects of drugs on cognitive and/or psychomotor tasks after controlled administration [2], [3], [4]. Others have investigated drugs effects in situations mimicking real driving such as driving simulators [5], [6] and closed or open-road driving trials [7]. All these studies highlighted the increased risk of road crashes for drivers under the influence of these drugs, but did not provide the magnitude of the problem nor quantify accident risk. It is the reason why a very large number of epidemiological studies have been performed in many countries. Most of them have been focused on the determination of the prevalence of drivers involved in fatal or non-fatal motor vehicle accidents while being under the influence of drugs. However, the value of a number of these studies in measuring how frequently do people drive under the influence of drugs is weak, because they did not use appropriate analytical procedures [8], i.e. determination of the active forms of the main DOAs in blood, using sensitive and specific analytical procedures, with appropriate cut-off values. In France, for example recent studies have shown that the potentially impairing compounds most frequently found in blood samples from drivers involved in fatal and non-fatal accidents are respectively alcohol, cannabinoids and benzodiazepines [9], [10], [11]. This finding has also been observed in many other countries. When they use appropriate methodology, these observational studies are of interest because their results can lead the concerned countries to undertake appropriate prevention actions. However, a better knowledge of the role played by drugs in the occurrence of accidents is afforded when drivers are compared to a control group, but such case-control studies have seldom been performed. An Australian case-control study performed in injured drivers [12] revealed a significant relationship between alcohol, benzodiazepines and responsibility for the car crash, but this relation was not significant for cannabinoids and stimulants. However, the cut-off used in blood for cannabinoids was 40 ng/ml, which is by far too high [13], since THC blood concentrations decline rapidly down to a few ng/ml while impairing effects are still present [14].

The present article reports the results of a French multicentre study whose aim was to compare the prevalence of alcohol, drugs of abuse (cannabinoids, amphetamines, cocaine metabolites and opiates) and psychoactive therapeutic drugs in blood in two groups: one of 900 injured drivers and other of 900 age- and sex-matched controls.

Section snippets

Materials and methods

The emergency care units (ECU) and toxicology laboratories from six French university or general hospitals participated in the study: Grenoble, Le Havre, Limoges, Lyon, Poitiers, and Strasbourg. Blood was used as the biological matrix to screen for alcohol, cannabinoids, opiates, cocaine metabolites, amphetamines and psychoactive therapeutic drugs. The samples were collected from June 2000 to September 2001.

Results and discussion

The distribution according to age is presented in Table 1. Females represented 25.7% of the drivers.

Conclusion

This study confirms the high prevalence of the use and/or abuse of psychoactive compounds in the French population [23], [24]. This is particularly true for cannabis in the young population. Furthermore, our results demonstrate a higher prevalence of alcohol, cannabinoids and the combination of these two compounds in blood samples from drivers involved in road accidents than in those from controls and consequently suggests a causal role for these compounds in road crashes. These findings

Acknowledgements

This study was carried out with financial support from the French Ministry of Health, in the framework of a “Programme Hospitalier de Recherche Clinique National”. The authors are indebted to Nicolas Venisse, Yves Papet, Fabrice Mairot, Gisèle Lardet, Gérard Musiedlak and Patricia Briquet for their technical and/or scientific assistance.

References (24)

  • P. Kintz, N. Samyn, A. Verstraete, Les prélèvements biologiques et techniques analytiques. In: P. Mura (Eds.), Alcool,...
  • M. Deveaux et al.

    Alcool et médicaments psychotropes dans les accidents mortels de la circulation

    Sem. Hôp. Paris

    (1991)
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