IOWA CITY, IA --- New research suggests that doctors may be able to use cognitive tests to help determine whether a person with Alzheimer's disease can still operate a car safely, reported.

"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," said study author Jeffrey Dawson with the University of Iowa in Iowa City. The research is published in the Feb. 10 issue of Neurology. The study was supported by the National Institute on Aging.

In the study, 40 drivers with early Alzheimer's disease and 115 elderly drivers without this diagnosis completed a series of off-road tests that measured thinking, movement and visual skills. The test participants also drove a 35-mile route in and outside the city. Driving safety errors were recorded by a driving expert, based on a video review of the drive.

The research found that drivers with Alzheimer's disease committed an average of 42 safety mistakes -- 27 percent more than the drivers without Alzheimer's disease, who made an average of 33 safety errors on the test drive. The most common mistakes were lane violations.

For every five years older the participant was, the number of safety errors rose by about two and a half, whether or not the driver had Alzheimer's disease. Among drivers with Alzheimer's disease, those who performed better on the off-road tests made fewer on-road safety errors.

"The goal is to prevent crashes while still maximizing patients' rights and freedom to be mobile," said Dawson. "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."