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University of Iowa News Release


Oct. 6, 2009

Note to Editors: This release is adapted in part from a release issued by the American Academy of Neurology
Photo: SIREN (Simulator for Interdisciplinary Research in Ergonomics and Neuroscience)

Parkinson's disease may increase crash risk in low visibility

sirenA study by researchers at the University of Iowa and the Iowa City Veterans Affairs (VA) Medical Center suggests that drivers with mild to moderate Parkinson's disease may be at higher risk of crashes compared to healthy older drivers in low visibility conditions such as fog.

The study used a driving simulator to compare driving abilities of 67 people with mild to moderate Parkinson's disease and 51 healthy people under conditions of low visibility. The findings were published in the Oct. 6 issue of Neurology, the medical journal of the American Academy of Neurology. 

"In addition to causing tremors and stiffness, Parkinson's disease also affects visual skills, such as the ability to see contrast and how fast people process what they see," said lead study author Ergun Uc, M.D., associate professor of neurology in the UI Roy J. and Lucille A. Carver College of Medicine and a staff physician at the Iowa City VA Medical Center. "We wanted to know if these visual deficits are associated with unsafe driving behaviors in patients with mild to moderate disease when they are driving in low visibility conditions."

Using a driving simulator to create different driving events and manipulate lighting conditions, participants, average age 67, drove first under clear sky and high visibility conditions, and then in a foggy, low visibility situation, leading up to an intersection where another vehicle posed a crash risk.

More people with Parkinson's disease were unable to avoid the crash compared to people without the disease -- 76 percent versus 37 percent. Their reaction time was also longer -- 2.7 seconds compared to 2.1 seconds. In addition, among drivers who crashed in the simulation, those with Parkinson's disease were driving at an average speed of 49 mph at the time of the crash compared to 39 mph for those who did not have Parkinson's disease.

"Our results suggest that a large proportion of drivers with Parkinson's disease may be at risk for unsafe driving in low visibility situations such as fog or twilight," Uc said.

Even during simulation segments with high visibility (clear sky) conditions, study participants with Parkinson's disease had more instances where the car's wheels crossed over the centerline or the shoulder line than people who did not have the condition, and their performance worsened as driving conditions changed from good to poor.

Among those with Parkinson's disease, those who performed the worst on the driving tests were those who had the lowest scores on tests of visual processing speed, motion perception, sensitivity to visual contrast and speed of movement.

The study was supported by the National Institute of Neurological Disorders and Stroke and the National Institute on Aging. In addition to Uc, the UI research team included Matthew Rizzo, M.D., professor of neurology, engineering and public policy; Steven Anderson, Ph.D., associate professor of neurology; Jeffrey Dawson, professor of biostatistics in the UI College of Public Health; and JonDavid Sparks and Elizabeth Dastrup graduate students in biostatistics.

STORY SOURCE: University of Iowa Health Care Media Relations, 200 Hawkins Drive, Room E110 GH, Iowa City, IA  52242-1009

MEDIA CONTACT: Jennifer Brown, 319-356-7124,