title: Driving under low-contrast visibility conditions in Parkinson disease.
abstract: 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.
authors.affiliation: Department of Neurology, University of Iowa, Carver College of Medicine, 200 Hawkins Dr., 2RCP, Iowa City, IA 52242, USA. ergun-uc@uiowa.edu
authors.forename: E Y
authors.initials: EY
authors.lastname: Uc
authors.forename: M
authors.initials: M
authors.lastname: Rizzo
authors.forename: S W
authors.initials: SW
authors.lastname: Anderson
authors.forename: E
authors.initials: E
authors.lastname: Dastrup
authors.forename: J D
authors.initials: JD
authors.lastname: Sparks
authors.forename: J D
authors.initials: JD
authors.lastname: Dawson
mesh_terms: D000063:Accidents, Traffic / Q000517:prevention & control / Q000523:psychology; D000368:Aged; D001334:Automobile Driving / Q000523:psychology; D016022:Case-Control Studies; D003071:Cognition; D015350:Contrast Sensitivity; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000503:physiopathology* / Q000523:psychology*; D011597:Psychomotor Performance; D011930:Reaction Time; D013647:Task Performance and Analysis; D014785:Vision, Ocular; D014796:Visual Perception