Determinants of On-Road Driving in Multiple Sclerosis

Objective To investigate the cognitive, visual, and motor deficits underlying poor performance on different dimensions of on-road driving in individuals with multiple sclerosis (MS). Design Prospective cross-sectional study. Setting MS clinic and driving simulator lab. Participants Active drivers (N=102) with various types of MS. Interventions Not applicable. Main Outcome Measures Off-road cognitive, visual, and motor functions, as well as 13 specific driving skills. These skills were categorized into hierarchic clusters of operational, tactical, visuo-integrative, and mixed driving. Stepwise regression analysis was used to determine the off-road functions influencing performance on the on-road test and each cluster. Results Visuospatial function (P=.002), inhibition (P=.008), binocular acuity (P=.04), vertical visual field (P=.02), and stereopsis (P=.03) best determined variance in total on-road score (unadjusted R²=.37). Attentional shift (P=.0004), stereopsis (P=.007), glare recovery (P=.047), and use of assistive devices (P=.03) best predicted the operational cluster (unadjusted R²=.28). Visuospatial function (P=.002), inhibition (P=.002), reasoning (P=.003), binocular acuity (P=.04), and stereopsis (P=.005) best determined the tactical cluster (unadjusted R²=.41). The visuo-integrative model (unadjusted R²=.12) comprised binocular acuity (P=.007) and stereopsis (P=.045). Inhibition (P=.0001) and binocular acuity (P=.001) provided the best model of the mixed cluster (unadjusted R²=.25). Conclusions Our results provide more insights into the specific impairments that influence different dimensions of on-road driving and may be used as a framework for targeted driving intervention programs in MS.