An explorative approach to understanding individual differences in driving performance and neurocognition in long-term benzodiazepine users

Objective: Previous research reported cognitive and psychomotor impairments in long‐term users of benzodiazepine receptor agonists (BZRAs). This article explores the role of acute intoxication and clinical complaints. Methods: Neurocognitive and on‐road driving performance of 19 long‐term (≥6 months) regular (≥twice weekly) BZRA users with estimated plasma concentrations, based on self‐reported use, exceeding the therapeutic threshold (CBZRA+), and 31 long‐term regular BZRA users below (CBZRA−), was compared to that of 76 controls. Results: BZRA users performed worse on tasks of response speed, processing speed, and sustained attention. Age, but not CBZRA or self‐reported clinical complaints, was a significant covariate. Road‐tracking performance was explained by CBZRA only. The CBZRA + group exhibited increased mean standard deviation of lateral position comparable to that at blood‐alcohol concentrations of 0.5 g/L. Conclusions: Functional impairments in long‐term BZRA users are not attributable to self‐reported clinical complaints or estimated BZRA concentrations, except for road‐tracking, which was impaired in CBZRA + users. Limitations to address are the lack of assessment of objective clinical complaints, acute task related stress, and actual BZRA plasma concentrations. In conclusion, the results confirm previous findings that demonstrate inferior performance across several psychomotor and neurocognitive domains in long‐term BZRA users

Sensitivity and validity of psychometric tests for assessing driving impairment: effects of sleep deprivation

OBJECTIVE: To assess drug induced driving impairment, initial screening is needed. However, no consensus has been reached about which initial screening tools have to be used. The present study aims to determine the ability of a battery of psychometric tests to detect performance impairing effects of clinically relevant levels of drowsiness as induced by one night of sleep deprivation. METHODS: Twenty four healthy volunteers participated in a 2-period crossover study in which the highway driving test was conducted twice: once after normal sleep and once after one night of sleep deprivation. The psychometric tests were conducted on 4 occasions: once after normal sleep (at 11 am) and three times during a single night of sleep deprivation (at 1 am, 5 am, and 11 am). RESULTS: On-the-road driving performance was significantly impaired after sleep deprivation, as measured by an increase in Standard Deviation of Lateral Position (SDLP) of 3.1 cm compared to performance after a normal night of sleep. At 5 am, performance in most psychometric tests showed significant impairment. As expected, largest effect sizes were found on performance in the Psychomotor Vigilance Test (PVT). Large effects sizes were also found in the Divided Attention Test (DAT), the Attention Network Test (ANT), and the test for Useful Field of View (UFOV) at 5 and 11 am during sleep deprivation. Effects of sleep deprivation on SDLP correlated significantly with performance changes in the PVT and the DAT, but not with performance changes in the UFOV. CONCLUSION: From the psychometric tests used in this study, the PVT and DAT seem most promising for initial evaluation of drug impairment based on sensitivity and correlations with driving impairment. Further studies are needed to assess the sensitivity and validity of these psychometric tests after benchmark sedative drug use

Single- and dual-task performance during on-the-road driving at a low and moderate dose of alcohol: A comparison between young novice and more experienced drivers

Driving experience and alcohol are two factors associated with a higher risk of crash involvement in young novice drivers. Driving a car is a complex task involving multiple tasks leading to dividing attention. The aim of this study was to compare the single and combined effects of a low and moderate dose of alcohol on single- and dual-task performance between young novice and more experienced young drivers during actual driving. Nine healthy novice drivers were compared with 9 more experienced drivers in a three-way, placebo-controlled, cross-over study design. Driving performance was measured in actual traffic, with standard deviation of lateral position as the primary outcome variable. Secondary task performance was measured with an auditory word learning test during driving. Results showed that standard deviation of lateral position increased dose-dependently at a blood alcohol concentration (BAC) of 0.2 and 0.5 g/L in both novice and experienced drivers. Secondary task performance was impaired in both groups at a BAC of 0.5 g/L. Furthermore, it was found that driving performance in novice drivers was already impaired at a BAC of 0.2 g/L during dual-task performance. The findings suggest that young inexperienced drivers are especially vulnerable to increased mental load while under the influence of alcohol

Mean baseline normalized performance at 1:00 am (16 hours awake), 5:00 am (20 hours awake) and 11:00 am (26 hours awake) compared with performance after a normal night of sleep (at 11:00 am) across dependent variables of the Digit Symbol Substitution Test, Concept Shifting Test, Determination Test, Useful Field of View Test, and Postural Balance Test.

<p>*p < 0.05, **p < 0.01, ***p <0.001. Error bars indicate the standard error of the mean.</p

Mean difference scores with 95% confidence intervals with performance after normal night of sleep, mean baseline^*-normalized z-scores, and effect sizes (Dunlap’s) of the performance tests.

<p>+ indicates moderate effect size;</p><p>++ indicates large effect sizes.</p><p>Abbreviations: RT = Reaction Time; z-AE = z-score of average tracking error; z-lg10(cl) = z-score of log transformed total number of control losses; z-RT = z-score of reaction time; z-log10(mi) = z-score of log transformed total number of misses; ln = natural log.</p><p>* baseline is performance after a night of normal sleep on a separate day.</p><p>Mean difference scores with 95% confidence intervals with performance after normal night of sleep, mean baseline^{<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0117045#t003fn004" target="_blank">*</a>}-normalized z-scores, and effect sizes (Dunlap’s) of the performance tests.</p