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Driving under low-contrast visibility conditions in Parkinson disease

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

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

Objective: To assess driving performance in Parkinson disease (PD) under low-contrast visibility conditions.

Methods: Licensed, active drivers with mild to moderate PD (n = 67, aged 66.2 ± 9.0 years, median Hoehn–Yahr stage = 2) and controls (n = 51, aged 64.0 ± 7.2 years) drove in a driving simulator under high- (clear sky) and low-contrast visibility (fog) conditions, leading up to an intersection where an incurring vehicle posed a crash risk in fog.

Results: Drivers with PD had higher SD of lateral position (SDLP) and lane violation counts (LVC) than controls during fog (p < 0.001). Transition from high- to low-contrast visibility condition increased SDLP and LVC more in PD than in controls (p < 0.01). A larger proportion of drivers with PD crashed at the intersection in fog (76.1% vs 37.3%, p < 0.0001). The time to first reaction in response to incursion was longer in drivers with PD compared with controls (median 2.5 vs 2.0 seconds, p < 0.0001). Within the PD group, the strongest predictors of poor driving outcomes under low-contrast visibility conditions were worse scores on measures of visual processing speed and attention, motion perception, contrast sensitivity, visuospatial construction, motor speed, and activities of daily living score.

Conclusions: During driving simulation under low-contrast visibility conditions, drivers with Parkinson disease (PD) had poorer vehicle control and were at higher risk for crashes, which were primarily predicted by decreased visual perception and cognition; motor dysfunction also contributed. Our results suggest that drivers with PD may be at risk for unsafe driving in low-contrast visibility conditions such as during fog or twilight.

Abbreviations: ADL = activities of daily living; CFT = Complex Figure Test; CS = contrast sensitivity; FOV = field of view; FR = functional reach; FVA = far visual acuity; JLO = judgment of line orientation; LVC = lane violation counts; PD = Parkinson disease; SDLP = SD of lateral position; SFM = structure from motion; SIREN = Simulator for Interdisciplinary Research in Ergonomics and Neuroscience; TFR = time to first reaction; UFOV = useful field of view; UPDRS = Unified Parkinson’s Disease Rating Scale.

Supplemental data at www.neurology.org

Supported by National Institute of Neurological Disorders and Stroke R01 NS044930 (Predicting Driver Safety in Parkinson’s Disease) to E.Y.U., and NIA R01 AG 17717 and NIA R01 AG 15071 to M.R.

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

Received March 3, 2009. Accepted in final form July 14, 2009.