TORONTO—New guidelines to help determine when patients with dementia should stop driving were presented at the 62nd Annual Meeting of the American Academy of Neurology. The guidelines, published in the April 20 Neurology, are based on a review of more than 6,000 published studies, making it the largest study of the topic to date.
“The sad truth is, as dementia progresses, there is going to be a point when the person is no longer able to drive,” said lead guideline author Donald J. Iverson, MD, Humboldt Neurological Medical Group Inc in Eureka, California. “It doesn’t happen in a single day. There’s no black and white transition from safe to unsafe driver; it’s a gradual process. This practice parameter identifies characteristics that identify patients who are at a higher risk for unsafe driving.”
Dr. Iverson noted that the gold standard for measuring driving safety is performance on a standardized on-the-road-driving test. The review found that people with mild dementia, defined as a Clinical Dementia Rating (CDR) score of 1, are 12 to 88 times more likely to fail a driving test.
“That sounds pretty bad. But on the other hand, there are studies that show 76% of patients with mild dementia were still able to pass a driving test,” he said. “In another study, 22% of the control group failed the driving test. So it is hard to come down with a categorical statement on this.”
The quality standards committee’s consensus is that patients with mild dementia should “strongly consider discontinuation of driving.” In addition, the board identified a number of situations that might indicate a patient is no longer a safe driver, and other factors that are not helpful in making that determination.
Patient and Caregiver Reports
When patients admit to their clinicians that their driving is a problem, it is a clear-cut indication that it is time for them to hand over the keys, according to Dr. Iverson. However, when patients say they are fine, that may not always be the case.
“Patients saying their driving is fine doesn’t necessarily reflect their driving ability,” Dr. Iverson said.
The same situation applies to family and caregivers. If they are concerned about a patient’s driving or do not want to be a passenger when the person drives, that correlates well with poor performance on a driving test. However, as with patient reports, an answer of “fine” does not always mean that all is well. “They may be trying to protect the patient, or not wanting to bear the burden of driving him or her around, or be in denial,” said Dr. Iverson.
Driving Habits
When a person older than 70 gets two or more traffic citations or is in more than one accident, that should also raise a red flag. “Citations and crashes are more important than just having dementia alone as far as determining unsafe driving,” Dr. Iverson reported. “Patients with two or more tickets [have] the highest driving risk—higher than 16-year-old boys.”
As their driving ability begins to decline, people tend to cut back on driving or avoid driving under certain circumstances, the researchers found. “As people age, they tend to drive less anyway. However, patients with dementia definitely reduce their driving more than their age-matched controls,” Dr. Iverson explained. “And this is an independent risk factor.”
The “magic number” is driving fewer than 60 miles a week, although “it’s hard to stick to that exact number as people are in different situations,” he said. “It is a guideline that reduced driving mileage is associated with poor performance on a driving test.”
Another tip-off is when patients say they will not drive in the rain or after dark. “Most of us would prefer to avoid driving in a storm, but when they always avoid it, that [signals] a risk factor for unsafe driving,” Dr. Iverson said. “Again, when patients say they are fine, it doesn’t automatically mean they are OK.”
Neuropsychologic Test Score
The researchers found that patients who had aggressive or impulsive personality characteristics—traits that may accompany certain types of dementia, including frontal-temporal dementia—have a higher risk for unsafe driving. However, the investigators were unable to identify any specific neuropsychologic test that provided additional prognostic information.
“A lot of dementia experts do these tests, particularly tests of visual and spatial abilities, which are not tested very well with routine screening exams,” Dr. Iverson noted. “A lot of seasoned clinicians believe they can use this information to identify patients at higher risk. We did not find evidence that is helpful.”
The researchers found some weak evidence that Mini-Mental State Examination (MMSE) scores may indicate a patient is at risk of unsafe driving; however, such scores are not fail proof. Although one study found that 64% of patients scoring 24 or less on the MMSE failed on the road driving tests, the remaining 36% passed. In addition, scoring 24 or higher does not guarantee that a person is a safe driver.