MONDAY, Feb. 9 (HealthDay News) -- The loss of driving privileges can be a blow to a person's independence, including people in the early stages of Alzheimer's disease.

Now, new cognitive tests may help doctors determine whether people with the illness are fit to drive.

University of Iowa researchers studied 40 drivers with early Alzheimer's disease and 115 elderly drivers with no diagnosis of dementia. All the participants completed a series of lab tests that measured thinking, movement and visual skills, and they also took a 35-mile driving test in and outside the city. A driving expert reviewed videos of the road tests and noted any driving safety errors.

The drivers with Alzheimer's committed an average of 42 safety mistakes, 27 percent more than the average of 33 safety errors made by those without Alzheimer's. Drivers with Alzheimer's who did better on the cognitive tests made fewer on-road safety mistakes, the team found.

Lane violations were the most frequent mistakes made by all participants. For every five years older the driver was, the number of safety errors increased by about 2.5, whether or not they had Alzheimer's.

The study is published in the Feb. 10 issue of Neurology.

"The number of people with dementia is increasing as our population ages, and we will face a growing public health problem of elderly drivers with memory loss," study author Jeffrey Dawson noted in an American Academy of Neurology news release.

"The goal is to prevent crashes while still maximizing patients' rights and freedom to be mobile. By measuring driver performance through off-road tests of memory, visual and motor abilities, we may be able to develop a standardized assessment of a person's fitness to drive," he said.

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