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

Movement Disorders
Volume 23 Issue 9, Pages 1217-1222 (15 July 2008)
Published Online: 4 June 2008

Authors: Richard Cordell, MBBS FRACP, Hoe C. Lee, PhD, Andrew Granger, MBChB FRACP, Barry Vieira, MBBS FRACP, Andy H. Lee, PhD

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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, R² = 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.

© 2008 Movement Disorder Society

Podcast review by Prof. Ergun Uc, MD, Associate Professor, University of Iowa

Parkinson's disease (PD) impairs cognitive, visual, and motor functions essential for safe driving. Establishing fair and accurate criteria to predict driving safety in PD will improve public safety by reducing the risk of motor vehicle crashes and help protect the independence of PD patients by avoiding unfair revocation of driving privileges.

This study aimed to investigate if severity of parkinsonism (as measured by the UPDRS scores, Hoehn-Yahr stage, and a timed walking test) and a "carer" questionnaire predicted the driving ability on a road test. Drivers had to be 60-80 years old. Subjects with MMSE scores less than 26 or decreased visual acuity or poor driving record were excluded from the study. IQ Code (Informant Questionnaire on cognitive decline) was used to assess cognitive status. No other performance based tests to assess cognition or visual perception were reported. The road test was given in the participant's car along a 15 km route chosen by the participant in his/her neighborhood. A driving instructor and an occupational therapist rated performance of the drivers across a range of driving conditions.

The study confirmed previously reported findings in the literature that the drivers with mild-moderate PD performed worse on road tests compared to controls, that they had a low insight into their driving ability, and that measures of severity of parkinsonism were of limited value in predicting driving performance. The carer questionnaire on the other hand correlated highly with the scores on the road test.

This study illustrates the potential value of a caregiver/informant questionnaire in predicting driving ability in PD. Future research to implement this questionnaire as a standard tool should include its validation in a broader segment of the PD driving population and determination of its predictive validity for real world unsafe driving outcomes such as at-fault crashes. Furthermore, it should be applied concurrently with standard performance based tests of cognition and visual perception to show its relative value in predicting driving ability, preferably on a standard route in an instrumented vehicle. A caregiver questionnaire as in this article may become a useful addendum to a future standardized evaluation battery on predicting driving ability in PD.

About Dr. Ergun Uc, MD

Dr. Uc is an Associate Professor at the Department of Neurology, Carver College of Medicine, University of Iowa, with a joint appointment at the VA Medical Center of Iowa City. He is a member of the American Neurological Association, American Academy of Neurology, Movement Disorder Society, Huntington Study Group, and Parkinson Study Group (PSG). Dr. Uc is the co-chair of the Cognition/Behavior Workgroup of the PSG and is a member of its Scientific Review Committee. He is the principal investigator of an ongoing NIH funded study on driver safety in Parkinson's disease (PD) and of a Veterans Affairs funded study on the effect aerobic exercise on cognition in PD.