Dec. 9, 2002 -- A growing body of scientific research is confirming what common sense implies -- Parkinson's patients can be dangerous behind the wheel. Yet aside from a doctor's suggestion, there is nothing to prevent most licensed patients with this degenerative disease to drive.
"The are no rules, laws, or regulations that concern driving for people with Parkinson's disease," says neurologist Abraham Lieberman, MD, medical director of the National Parkinson's Foundation and a professor of neurology of the University of Miami School of Medicine. "The issue of driving and Parkinson's disease is one that has been looked into, but never in a way as seriously as with epilepsy. And I'm not sure that it will anytime soon."
But the latest study on the issue, published in the Dec. 10 Neurology, suggests that perhaps it should. Researchers found a direct link in the likelihood of driving accidents with the disease's progression. Nearly all of the 39 Parkinson's patients who were tested in a driving simulator were involved in collisions. And while most of them admitted the disease made it harder to operate a car, half continued their pre-diagnosis driving habits with no reduction in time behind the wheel.
"What was surprising, based on our and previous studies, is that the patients didn't have a good feeling or understanding on how bad their driving really was," says lead researcher Theresa A. Zesiewicz, MD, of the Parkinson's Disease and Movement Disorders Center at the University of South Florida College of Medicine. "But I wasn't surprised by the (accident) results."
Those who still drove regularly and had accidents during the test were older and had more advanced disease. "We found it particularly interesting that there was no relationship between Parkinson's patients' self-reporting of moving violations and their total collisions on the driving simulator."
Zesiewicz' study comes just six months after Austrian researchers reported that one in three Parkinson's patients in their study suffered from medication-caused attacks that caused them to suddenly fall asleep. That finding, in the British Medical Journal, backs a 1999 report by neurologist Steven Frucht, MD, that first implicated the drugs with sudden sleep attacks. In his paper, he noted that eight Parkinson's patients studied actually fell asleep behind the wheel.
"My own view: There should be established rules concerning Parkinson's patients and their right to drive," Frucht tells WebMD. "Prior studies show that even patients with mild Parkinson's have unrecognized driving deficits. But this is a very touchy subject."
Parkinson's is caused by a gradual but steady deterioration of nerves in the part of the brain that controls movement, causing muscle rigidity, tremors, poor balance and slowness in movement and reaction. In later stages, it can cause memory loss. It affects about 1 1/2 million Americans, usually after age 50.
While numerous studies have shown that the disease does impair driving -- by the disease itself and the medication to treat it -- efforts even to bring up the issue are usually rare, says Zesiewicz.
"We don't want to bring it up," she tells WebMD. "Patients love to drive and it increases their quality of life; it gives them independence. When doctors broach the driving topic, it's met with resistance -- by the patients and their families. I think many doctors are unaware of the problem, but others may feel they'll be unpopular with their patients."
There is also debate on when Parkinson's severely impacts driving ability, and some question how it compares to deficits caused by normal aging. In Zesiewicz's study, for instance, 20% of both early-stage Parkinson's patients and "healthy" seniors at the same age caused simulated accidents.
"There have been studies finding that age had more influence on driving ability, or the lack of it, than early or middle stages of Parkinson's," says Judy Rosner, a spokeswoman for the Parkinson's Disease Foundation. "I don't think you can establish driving guidelines because this disease affects different people in different ways. Our recommendation is, if you are concerned about a family member, bring them in for testing. Let the appropriate officials decide if they are able to drive."
Ellie Martin, a spokeswoman for the federal National Highway Traffic Safety Administration, says her agency has "no opinion" on whether Parkinsonians should have driving restrictions. "Any and all laws pertaining to who can drive and who can't are decided by the individual state," she tells WebMD.
"However, we have new advanced driving simulators, under the management of the University of Iowa, that tests drivers with various medical conditions to determine how these illnesses and medications impact their ability to drive. One of the potential uses is for those with Parkinson's disease. But as far as I know, no studies are scheduled." The university confirmed no Parkinson's studies are under way or planned.