Elsevier

Accident Analysis & Prevention

Volume 60, November 2013, Pages 31-34
Accident Analysis & Prevention

Short communication
Lorazepam impairs highway driving performance more than heavy alcohol consumption

https://doi.org/10.1016/j.aap.2013.08.004Get rights and content

Highlights

  • We compared benzodiazepine (BZD) intake with blood alcohol concentration (BAC).

  • 16 participants underwent a 2-h driving paradigm in real-world and simulated settings.

  • Weaving (SDLP) and inappropriate line crossings were higher in the simulator.

  • The SDLP increment after BZD equalled high BAC values in both real and simulated conditions.

  • We recommend that physicians be made more aware of BZD-related risks.

Abstract

While research indicates that benzodiazepine (BZD)-like drugs impair driving performance, it remains unclear (i) how far BZDs affect lane-keeping performance, compared with alcohol and (ii) to what extent this impact can realistically be measured in a simulated environment. To clarify these issues, 16 healthy male drivers who had never previously taken BZDs underwent a randomized, crossover, double-blind, placebo-controlled driving paradigm (with the BZD lorazepam) in both real-world and simulated settings. Two lane-keeping variables, namely inappropriate line crossings (ILCs) and standard deviation of lateral position (SDLP), were recorded during the driving sessions. Analyses revealed that (i) a single lorazepam dose (2 mg given by mouth) caused higher SDLP increases than a blood alcohol concentration of above 0.05%, and that (ii) this BZD effect was amplified in the simulated driving setting, mainly for ILCs. As a consequence, we recommend that physicians be made more aware of BZD-related risks and that researchers make a clear distinction between the effects of BZD intake per se and the impact of simulated driving settings.

Introduction

In many countries, benzodiazepine (BZD)-like drugs are the most commonly used and misused psychoactive medicinal drugs (Kriikku et al., 2012). BZDs are widely used as anxiolytics and hypnotics. However, as well as bringing benefits, BZDs can also produce side effects, such as daytime sedation, reduced alertness and cognitive impairment. Importantly, the effects of BZDs on both attentional processes and the general level of psychomotor activity can prove dangerous while performing everyday tasks such as driving (e.g., Törnros and Laurell, 1990, Leufkens et al., 2007).

In their meta-analysis of studies of the effects of BZDs on accident risk, Rapoport et al. (2009) found that summary estimates of the odds ratio of accident involvement for BZD users were 1.61 for case–control studies and 1.60 for cohort studies – figures close to those reported by Dassanayake et al. (2011). In their review of research on the risks associated with the use of medicinal drugs, Orriols et al. (2009) also concluded that BZD use is associated with an increased risk of accident, with no evidence of any such risk for other medicinal drugs. It has been argued that the higher the BZD blood concentration, the higher the proportion of drivers assessed as impaired, which is reminiscent of the relationship between alcohol and impairment (Bramness et al., 2002, Vermeeren et al., 2002, Smink et al., 2008, Gustavsen et al., 2009).

The purpose of this study was thus to explore the effects of BZDs on driving safety, focusing on the trajectory control component of driving performance (i.e., lane-keeping). Although the latter was assessed using two classic measures, namely the standard deviation of lateral position (SDLP) and the number of line-crossings (e.g., Dijksterhuis et al., 2011), the study was designed to make two novel contributions.

First, we set out to determine how far BZD-related changes in lane-keeping can be quantified. Research suggests that the effects of different variables on lane-keeping can best be gauged by comparing them with changes in lane-keeping brought about by (higher) BAC levels (Menzin et al., 2001, Ramaekers, 2003, Verster et al., 2011). However, while this type of information about BZDs would presumably be useful in different policy settings, such comparisons have been made only scarcely (Verster et al., 2002, Leufkens et al., 2007).

Second, it seemed relevant to assess the impact of BZDs not only in the real world but also in simulated driving settings. Arguably, evaluating how close the impact of BZDs on driving a simulator is to that observed in real-world settings would make it possible to avoid costly on-road tests. Yet, studies directly comparing drug impairment in these two driving environments are scarce (e.g., Helland et al., 2012) and, when it comes to BZDs, seemingly nonexistent.

In sum, then, the general aim of this study was to complement existing knowledge regarding the impact of BZDs on driving performance. More specifically, we looked at (i) how much BZD intake impairs lane-keeping performance when quantified through comparison with BAC levels and (ii) the degree to which this impact can be realistically measured in a simulated environment. To this end, a randomized, crossover, double-blind, placebo-controlled study with the BZD lorazepam was replicated in both real-world and simulated settings (e.g., Verster & Roth, 2011).

Section snippets

Participants

Sixteen healthy male volunteers, aged 25–35 years (M = 29.79 years, SD = 3.45), were recruited for the purpose of this study. They were not taking any medication that might interfere with the experimental BZD treatment, and presented neither sleep-related disorders nor acute or chronic pathologies. All the participants had been in possession of their driving licence for at least three years (M = 11.43 years, SD = 4.77), had no reliable variability in their driving experience (driving almost every day

Results

After examining the sleepiness self-ratings provided before each driving session, we analyzed the participants’ driving performance (ILCs, SDLP). The mean values, as well as both the main and interaction effects, are summarized in the tables. We conclude our analysis by estimating the BAC level corresponding to the changes in SDLP observed after BZD intake.

Discussion

Our experimental study clearly shows that drivers’ lane-keeping is worse when driving under BZD than under placebo, confirming the results of previous studies (Willumeit et al., 1984, Brookhuis et al., 1990; for a review, see Orriols et al., 2009). Interestingly, this dosage and type of drug (i.e., single 2-mg dose of lorazepam), to be taken in the morning, is a very common prescription for treating anxiety. It is also worth noting that epidemiological studies of hypnotics like BZD (taken at

Conclusion

The major contribution of this study is the finding that even a 2-mg dose of lorazepam can cause an increment in weaving that far exceeds the increments induced by alcohol consumption within known legal limits. Physicians must bear these side effects in mind when prescribing lorazepam, especially for the very short treatment periods that are now recommended for many BZDs by the French drug agency (ANSM). This study further reveals that simulated driving settings may magnify drivers’

Acknowledgments

We would like to express our gratitude to the French National Research Agency (Agence Nationale de Recherche) for funding the present study (Grant No. ANR-05-PDIT-012-05). We also wish to thank Clinique Spatiale (MEDES IMPS Toulouse) for its collaboration on the simulator-related part of the experiment. We finally thank Elizabeth Portier for revising the English style.

References (24)

  • T.R. Leufkens et al.

    Cognitive, psychomotor and actual driving performance in healthy volunteers after immediate and extended release formulations of alprazolam 1 mg

    Psychopharmacology

    (2007)
  • S.G. Leveille et al.

    Psychoactive medications and injurious motor vehicle collisions involving older drivers

    Epidemiology

    (1994)
  • Cited by (0)

    View full text