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 Volume 73, Number 24, December 15, 2009
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NEUROLOGY 2009;73:2112-2119
© 2009 American Academy of Neurology

Road safety in drivers with Parkinson disease

E. Y. Uc, MD, M. Rizzo, MD, A. M. Johnson, MS, E. Dastrup, MS, S. W. Anderson, PhD and J. D. Dawson, ScD

From the Department of Neurology (E.Y.U., M.R., S.W.A.), Department of Mechanical and Industrial Engineering (M.R.), Public Policy Center (M.R.), and Department of Biostatistics (A.M.J., E.D., J.D.D.), University of Iowa, Iowa City; and Neurology Service (E.Y.U.), Veterans Affairs Medical Center, Iowa City, IA.

Address correspondence and reprint requests to Dr. Ergun Y. Uc, Department of Neurology, University of Iowa, Carver College of Medicine, 200 Hawkins Drive-2RCP, Iowa City, IA 52242; ergun-uc{at}uiowa.edu

Objective: To assess road safety and its predictors in drivers with Parkinson disease (PD).

Methods: Licensed, active drivers with PD (n = 84; age = 67.3 ± 7.8, median Hoehn & Yahr stage II) and controls (n = 182; age = 67.6 ± 7.5) underwent cognitive, visual, and motor tests, and drove a standardized route in urban and rural settings in an instrumented vehicle. Safety errors were judged and documented by a driving expert based on video data review.

Results: Drivers with PD committed more total safety errors compared to controls (41.6 ± 14.6 vs 32.9 ± 12.3, p < 0.0001); 77.4% of drivers with PD committed more errors than the median total error count of the controls (medians: PD = 39.5, controls = 31.0). Lane violations were the most common error category in both groups. Group differences in some error categories became insignificant after results were adjusted for demographics and familiarity with the local driving environment. The PD group performed worse on tests of motor, cognitive, and visual abilities. Within the PD group, older age and worse performances on tests of visual acuity, contrast sensitivity, attention, visuospatial abilities, visual memory, and general cognition predicted error counts. Measures of visual processing speed and attention and far visual acuity were jointly predictive of error counts in a multivariate model.

Conclusions: Overall, drivers with Parkinson disease (PD) had poorer road safety compared to controls, but there was considerable variability among the drivers with PD, and some performed normally. Familiarity with the driving environment was a mitigating factor against unsafe driving in PD. Impairments in visual perception and cognition were associated with road safety errors in drivers with PD.

Abbreviations: ADL = activities of daily living; AVLT = Auditory Verbal Learning Test; BVRT = Benton Visual Retention Test; CFT = Complex Figure Test; COWA = Controlled Oral Word Association; CS = contrast sensitivity; ESS = Epworth Sleepiness Scale; FVA = far visual acuity; GDS = Geriatric Depression Scale; JLO = Judgment of Line Orientation; MMSE = Mini-Mental State Examination; NVA = near visual acuity; NS = nonsignificant; PD = Parkinson disease; SE-ADL = Schwab-England Activities of Daily Living; SFM = Structure from Motion; UFOV = useful field of view; UPDRS = Unified Parkinson's Disease Rating Scale.

Supplemental data at www.neurology.org

Disclosure: Author disclosures are provided at the end of the article.

Received June 6, 2009. Accepted in final form October 6, 2009.