Study Looks at Ability to Drive in Patients with Azheimer’s, Other Cognitive Impairments

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Toronto researchers have examined the driving ability in people with cognitive impairments, including those with Alzheimer’s disease. The recent report, A Systematic Review and Meta-Analysis of On-Road Simulator and Cognitive Driving Assessment in Alzheimer’s Disease and Mild Cognitive Impairment, appeared in the Journal of Alzheimer’s Disease.

Led by Megan Hird of the Neuroscience Research Program at St. Michael’s Hospital in Toronto, Canada, investigators hoped to understand if cognitive tests predict driving ability in people with Alzheimer’s disease and mild cognitive impairment. The team reviewed the existing medical literature on driving assessment methods that used tests such as actual on-road driving, cognitive tests, and driving simulations. The authors then tried to find which tests were best for detecting driving difficulties.

The review and meta-analysis included 32 articles, including 1,293 subjects with Alzheimer’s disease (AD), 92 subjects with mild cognitive impairment, and 2,040 healthy people with neither problem.

There were several statistically significant predictors of driving performance. These included global cognition, visuospatial function, and attention and executive function. Two tests were the most effective for predicting driving performance: the Trail Making Test part B and the Maze test. In the Trail Making Test part B, a person is asked to connect alternating encircled numbers and letters. This assesses visual attention and ability to change tasks. The Maze test involves the use of drawn mazes to measure planning and foresight.

Hird and her colleagues also found that even people with very mild Alzheimer’s disease are more likely to fail a driving test compared to healthy control subjects. They concluded that “the driving ability of patients with [mild cognitive impairment] and AD appears to be related to degree of cognitive impairment. Across studies, there are inconsistent cognitive predictors and reported driving outcomes in [mild cognitive impairment] and Alzheimer’s patients.”

The study provides some information about driving ability and cognition, but more studies with greater specificity are still needed. For example, the effect of mild cognitive impairment needs to be studied in more depth. Fewer studies of mild cognitive impairment have been performed by scientists overall compared with studies of Alzheimer’s and driving ability.

Guidelines from the American Academy of Neurology (AAN) have their own standard for detecting whether someone with mild congitive impairment should drive. The ANN states that a mini state exam score of 24 or less shows that there is a risk of unsafe driving.

AAN guidelines also suggest that caregivers can play a critical role in assessing whether someone with cognitive impairment should drive.