Driving assessment in Parkinson's disease--a novel predictor of performance?

Clinical symptoms of Parkinson's disease (PD) can make driving hazardous. The removal of the privilege to drive reduces independence; nevertheless, to protect public safety, medical practitioners require reliable screening tools to decide whether a PD driver should be on the road. The aims of this study were to examine whether clinical measures for PD patients and information provided by carers can be employed to predict impairment in driving performance. Fifty three idiopathic PD subjects and 129 age-matched controls were assessed on open roads. Prior to the driving assessment, participants were examined by a geriatrician. Various clinical measures of PD were recorded, and their carers filled out a questionnaire assessing driving ability of the patient. The driving performance of the participants declined with age (r = 0.89, P < 0.001). Drivers with PD were significantly less competent drivers than controls. The commonest errors committed on the road were indecisiveness in T-junctions and reduced usage of rear view and side mirrors. Only two of the clinical measures of PD patients showed links to driving performance. Information provided by carers was significantly related to driving performance of PD patients (F((4,48)) = 3.87, P-value < 0.01, R(2) = 0.557). PD drivers were less competent drivers than the age-matched control group; moreover, standard clinical measures of PD have little value in predicting their driving performance. Carers can provide valuable information to doctors in identifying unsafe PD drivers.