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NEW YORK (Reuters Health) - The thinking and muscle problems commonly caused by Parkinson's disease hamper driving skills in most elderly people with the progressive brain disorder, new study findings confirm.
However, there is "considerable variability" in driving performance among elderly Parkinson's patients; some can operate a motor vehicle as safely as age-matched individuals without the disease, the study found.
Parkinson's disease is complex and multifaceted, study leader Dr. Ergun Y. Uc noted in comments to Reuters Health, and he advises patients with the disease to talk to their doctor about driving safety. When it comes to driving, "every patient should be evaluated individually," the researcher said.
Parkinson's disease is a degenerative brain disease that causes body tremors, rigid muscles, and difficulty walking and talking.
Uc, of the University of Iowa and the Veterans' Affairs Medical Center, both in Iowa City and colleagues compared visual, physical, and thinking skills, plus driving abilities in licensed, active, community-living men and women who were about 67 years old on average - 84 with mild to moderate Parkinson's disease and 182 without the disease.
About 77 percent of the drivers with Parkinson's made more errors at stop signs, with lane changes and turning, and had more difficulty controlling speed and staying in their lane compared with their counterparts without the disease.
But about 23 percent of drivers with Parkinson's disease drove as safely as the best disease-free drivers, Uc's team reports in the journal Neurology.
In the study, a professional driving instructor evaluated video recordings of each participant's 45-minute venture over a set route of country and city, 2- and 4-lane roadways in a car outfitted with hidden sensors.
Uc's team cautions, however, "this road test did not include any sudden hazards," when reaction time is critical.
Overall, drivers with Parkinson's disease were about twice as likely to commit serious driving errors such as entering an intersection on a red light or not stopping at a stop sign.
Familiarity with the roadways seemed to minimize driving errors; thinking and vision problems seemed most predictive of poor driving.
These latest findings build on two other studies conducted by Uc's team. One showed that people with Parkinson's disease have difficulty spotting traffic signs and roadside landmarks while driving, and are more likely to make safety errors on the road. The other found that multitasking while driving -- such as talking to a passenger or on a cell phone -- puts drivers with Parkinson's disease at higher risk of driving errors than Parkinson's-free drivers.
Uc is currently spearheading a National Institutes of Health-funded study of Parkinson's patients with the goal of developing a system to predict their driving abilities.
SOURCE: Neurology, published online December 16, 2009
