Neurologists weigh in on cognitive impairment, driving

Apr 13 2010 - 8:45pm

WASHINGTON -- Taking the car keys away from an aging parent or spouse whose mental faculties are slipping is one of the most difficult decisions a loved one confronts. But sometimes, it must be done. And knowing what checklist neurologists use might help both to back up your judgment and take some of the sting out of the decision for all parties.

Fortunately, the American Academy of Neurology has just issued new practice parameters for physicians that take account of the most recent findings on cognitive impairment and driving. This is the group's first update of the document in a decade.

Among patients who have recently been diagnosed with mild dementia, 76 percent can still pass an on-road driving test. Clearly, some with mild dementia can continue for some time to drive safely, but not all.

The stakes for guessing which ones should not are high. But "there is no test result or historical feature which accurately quantifies driving risk," the academy says. The neurologist's most useful tool for gauging dementia is called the mini-mental state exam, but a patient's score on that test alone is not a good predictor of an older driver's ability to drive safely.

The academy recommends that, beyond a patient's performance on the mini-mental state exam, a physician should consider the patient's past driving record, his or her level of aggressiveness and impulsiveness, and whether the patient acknowledges avoidance in his or her driving patterns -- reporting, for instance, that he stays away from driving on highways or at night. When the driver acknowledges such avoidance behavior, that's a more useful clue than when she doesn't; some patients don't respond to declining driving performance by scaling back.

In the same vein, eliciting a caregiver's view of a patient's driving safety is most useful to a physician in cases where the caregiver rates the patient's driving as marginal or unsafe. Recent research suggests that caregivers routinely overestimate the driving performance of a loved one with dementia -- a fact that loved ones should consider when they begin to have doubts.

And taking a patient's word for it is clearly not useful. The practice guidelines took note of research finding that in a group of patients with mild Alzheimer's disease, 94 percent identified themselves as safe drivers, while only 41 percent could actually pass an on-road driving test. Another study of drivers diagnosed with mild Alzheimer's found that all of those who had failed the on-road driving exam had rated themselves as good drivers.

Sadly, there are no proven interventions -- classes, medications, strategies -- that can reduce driving risk for those with dementia. One study suggested that requiring those over 85 years of age to come in and apply for a license in person reduced fatal crashes among this population.

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