ARTICLE IN BRIEF
An analysis based on 50 previously published studies on Parkinson's patients and driving found that while Parkinson's patients were no more likely to report being in a crash than healthy controls, they were more likely to fail simulator driving tests or on-road driving assessments.
The question of whether to give up driving is often an emotional topic for Parkinson's patients and families. Not driving can mean a loss of independence and convenience. But continued driving could be dangerous for someone experiencing cognitive and motor decline, as well as for the people they encounter on the road.
The driving issue also can be an uncomfortable conversation for doctors, who want to encourage their Parkinson's disease (PD) patients to keep active and engaged in life while staying safe. A new study, published online first on August 3 in Neurology, may help inform those difficult discussions, though it doesn't provide all the answers.
The study, a meta-analysis, was based on 50 previously published studies on Parkinson's patients and driving. It found that while Parkinson's patients were no more likely to report being in a crash than healthy controls, they were more likely to fail simulator driving tests or on-road driving assessments.
Why the seemingly disparate findings? It may be that Parkinson's patients simply stop driving or compensate by sticking to familiar routes, making it less likely they will get in an accident. On the other hand, the driving simulator and on-road tests could reveal some concerning deficits in skills required for driving that may not be obvious in the doctor's office.
Trevor Thompson, PhD, the study's lead author and a senior lecturer and health researcher at University of Greenwich in England, said the study results suggest there is not a one-size-fits-all approach when it comes to Parkinson's and driving.
“While neurological disorders such as PD clearly decrease the ability to perform certain activities such as driving, that does not always mean that activity has to be given up,” Dr. Thompson said in an email to Neurology Today. But that said, the decision on whether to continue or stop driving must factor in all sides of the argument, from the effect on the patient's quality of life to the ramifications should an accident happen.
“Doctors are well aware any recommendation to stop driving can't be taken lightly,” Dr. Thompson said. “Nevertheless, this is a public safety issue that — as with anything that may affect fitness to drive — needs to be considered,” he said.
`Ergun Y. Uc, MD, professor of neurology and director of the Division of Movement Disorders at the University of Iowa and the senior author of the new meta-analysis, said the findings align with earlier studies he has conducted that show that PD patients perform worse on road and simulator testing, and tend to give up driving before anything awful happens.
“You would expect that Parkinson's patients would crash more in real life because they are crashing more in the simulator or fail in road testing, but they are stopping driving much earlier than their healthy peers so they are not on the road anymore to suffer crashes,” Dr. Uc said.
He said it is difficult to make a “cookbook recommendation” because PD is a long-lasting illness and symptoms manifest differently from patient to patient. Cognition, vision, and balance problems may be more of an issue for driving than mild tremors. He said some younger patients with preserved cognition might be able to continue driving for many years.
Dr. Uc, who directs the Parkinson's Foundation Center of Excellence at Iowa, is planning research that will use “black boxes” installed in patients' cars to see what happens in everyday driving. He said naturalistic assessments might identify what symptoms and circumstances are most problematic.
The study, which involved researchers from six institutions and four countries, noted that PD symptoms, including motor instability, increased response time, attentional deficits, visual impairment, daytime sleepiness and medication-exacerbated sleep attacks “may compromise capacity to drive.” Safety concerns have led to “recent policy debate over the need for mandatory based revaluation of fitness to drive in those with degenerative diseases.”
The researchers pooled data from 50 studies that included 1,955 PD patients and 3,455 controls. They found that the odds of failing an on-road driving test were more than six times greater for PD patients compared to controls and the odds of crashing during a driving simulator test were more than 2.5 times greater, with overall driving ratings also lower for PD patients. However, PD patients did not self-report real-life crashes any more than controls.
The researchers said duration and severity of illness did not seem to influence those outcomes, though Dr. Thompson warned that those findings should be viewed cautiously because of the type of data available for the meta-analysis.
“Our findings provide persuasive evidence for substantive driving impairment in PD,” the researchers concluded, “but offer little support for mandated PD-specific re-licensure based on self-reported crash data alone, and highlights the need for objective measures of crash involvement.”
Dr. Thompson noted that “the law in the U.K. is that you must tell the licensing agency (and your insurer) if you have been diagnosed with PD,” and then the licensing agency reassesses the person's abilities to determine fitness to drive.
“There do not appear to be any state driving laws specific to PD in the US, though several states have laws related to the reporting of drivers with cognitive impairment and/or seizure disorders.
Cynthia L. Comella, MD, FAAN, professor of neurological sciences at Rush University Medical Center, said she was surprised that the study found that duration and severity of PD illness did not appear to increase the risk of crash, in testing or real life.
“There is clearly a difference in Parkinson disease when going from stage 2 to stage 3,” she said. “One would have anticipated worsening in driving skills with the increasing disability.”
Dr. Comella, who specializes in movement disorders, routinely discusses driving with PD patients and strives to be frank.
“I ask the patient ‘Do you feel safe behind the wheel? If you are driving and a child walks in front of the car, do you worry you could injure the child?’” she said. She also asks family members of the patient if they feel safe when they are in the car. There could be legal and financial ramifications if someone has a car accident, not to mention guilt if someone gets hurt or killed.
It is not unusual for patients to be resistant to the idea of giving up driving, Dr. Comella said. She sometimes gets push back, for instance, if a patient relies on their car to get to work, but often family members are relieved she is asking the questions because they are concerned and would like to take away the keys.
Dr. Comella, who is opposed to mandatory driving retesting and reporting for PD, said some patients “edit themselves, where they go, when they go. They drive locally, to the store,” but that might still be risky. If a patient exhibits troubling signs, she suggests a driving evaluation, which provides an objective assessment that is hard to argue with.
Dr. Comella said there is no debate if a patient has gotten into a crash. She said that luckily there now are more driving alternatives, such as Uber and Lyft, though such services may be too expensive for some patients or not widely available where they live.
Irene Litvan, MD, FAAN, professor of neurology and director of the Parkinson & Other Movement Disorders Center at University of California San Diego, said it is important for doctors caring for PD patients to do periodic neuropsychological assessments, perhaps every six months, to look for signs of cognitive impairment that could impact driving. Deficits may not stand out in a routine checkup.
Some PD patients with mild cognitive impairment might still be OK to drive, particularly in familiar surroundings, Dr. Litvan said. She said doctors are required by law in California to report patients to the Department of Motor Vehicles if they have dementia or other problems that could make them unsafe behind the wheel. A driving re-evaluation is then ordered.
Lissa Kapust, LICSW, social work program manager at the DriveWise driving evaluation center at Beth Israel Deaconess Hospital, said giving up driving can be hard on patients. Having alternatives in place helps with the transition.
“It is a defining moment,” she said. “I think as long as the person can still drive life seems pretty normal. But the moment a person's license is jeopardized, suddenly the illness moves to the front burner and defines them as someone who is sick.”
Doctors may be reluctant to question a patient about driving because they feel they don't have the expertise or time to address the complicated issue, said Margaret O'Connor, PhD, a neuropsychologist who is associate professor of neurology at Harvard Medical School and directs research at the DriveWise program.
One challenge for doctors for is that PD symptoms can fluctuate and what they observe in the office may not reflect whether the patient can do the multitasking required for driving. Medication levels, attention, mood, reaction time, and motor skills, among other things, all can play a role.
“A lot of them (PD patients) drive quite well,” Dr. O'Connor said.
She said that while it makes sense to think that initiating mandatory reporting and retesting for people with significant cognitive impairment (which would include some PD patients) may be the way to decrease auto accidents — several states have gone that route — research is beginning to show that such laws don't necessarily result in fewer crashes.