UNSAFE BEHIND THE WHEEL?
DRIVING SAFETY IN PATIENTS
WITH PARKINSON'S DISEASE

SAN DIEGO—The ability of patients with Parkinson's disease to drive may be overestimated by both the patients and their neurologist, according to Theresa A. Zesiewicz, MD. "Patients with advancing disease may need evaluation by a driving instructor or a driving simulator to assess their safety to drive," she said at the 52nd Annual Meeting of the American Academy of Neurology.

Dr. Zesiewicz, Robert Hauser, MD, and colleagues evaluated the driving ability of 39 patients with Parkinson's disease (mean age, 65.6) and 25 controls (mean age, 64.9). The participants underwent a Mini-Mental State Exam, Trailmaking B Test, and a self-report questionnaire about their driving history. Additionally, participants with Parkinson's disease underwent "on" Unified Parkinson's Disease Rating Scale (UPDRS) evaluation and Hoehn and Yahr staging immediately before testing. The average Hoehn and Yahr score for Parkinson's disease patients was 2.10. The researchers measured the participants' driving ability by the number of "day" and "night" collisions registered by the driving simulator. Dr. Zesiewicz is Assistant Director of the Parkinson's Disease and Movement Disorders Clinic at the University of South Florida, Tampa.

A GREATER RISK OF COLLISION

Parkinson's disease patients had more simulator collisions than controls had, the researchers found. The difference (mean, 1.25 versus 0.2) was statistically significant, said Dr. Zesiewicz. No significant correlation was found between number of accidents and nighttime driving or sleepiness. She added that most accidents occurred at the first intersection of the driving test.

Data also indicated that patients with more severe Parkinson's disease were more likely to be involved in simulator collisions. Risk of collision was significantly associated with Trailmaking B time to completion score (r = .477), UPDRS motor score, (r = .487), and Hoehn and Yahr score (r = .507). Twenty percent of Hoehn and Yahr stage 1 participants, 56% of stage 2 participants, 90% of stage 3 participants, and 100% of stage 4 participants were involved in at least one collision. Dr. Zesiewicz noted that neither dyskinesia nor tremor was associated with risk of collision. The study did not control for medication, nor did it indicate a correlation between side of involvement and side of accident.

OBJECTIVE OPINION MOST ACCURATE

Some Parkinson's disease patients had already restricted their own driving: 18% had stopped altogether, and 26% had decreased their driving. Among Parkinson's disease patients who had restricted their driving, 20% cited concentration difficulties and 30% cited stiffness as the primary reason for the restriction. Although some patients with Parkinson's disease had restricted their own driving, there was no correlation between self-report of driving ability and simulator collisions. This indicates that patients may not be able to adequately evaluate their own driving, she said, and neurologists may be overestimating the patients' driving ability. "We are following the subjects in this study to determine how well driving simulator results predict accidents in [Parkinson's disease] patients," concluded Dr. Zesiewicz.

EVALUATION VIA MANY METHODS

A previously published study by researchers at the Merikoski Research and Rehabilitation Centre, Oulu, Finland, also indicated that neither patients with Parkinson's disease nor their neurologists could accurately evaluate their standard of driving. During the study, 20 patients with Parkinson's disease and 20 controls were evaluated by a neurologist, a psychologist, a vocational rehabilitation counselor, and a driving instructor, using a 10-point scale. As Dr. Zesiewicz and colleagues also found, the patients with Parkinson's disease performed worse than controls on the driving test; however, the Finnish study did not indicate that severity of disease correlated with test score.

While driving ability is greatly decreased in patients with Parkinson's disease, the evaluation of patients' driving ability is difficult to accurately assess without psychological and psychomotor tests. Patients and physicians should seek additional professional assistance in determining a patient's driving competence, Dr. Zesiewicz concluded.

—Kathryn Blair
Associate Editor

Suggested Reading
Cox DJ, Taylor P, Kovatchev B. Driving simulation performance predicts future accidents among older drivers. J Am Geriatr Soc. 1999;47:381-382.
Heikkila VM, Turkka J, Korpelainen J, et al. Decreased driving ability in people with Parkinson's disease. J Neurol Neurosurg Psychiatry. 1998; 64:325-330.

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