NEW YORK (Reuters Health) - Older people who drive are more likely to restrict their motor vehicle use or even stop driving entirely if they are experiencing certain types of visual and cognitive problems, new research shows.

The findings are "reassuring," Dr. Lisa Keay of Johns Hopkins University in Baltimore and her colleagues state in their report. "These data suggest drivers with functional deficits make difficult decisions to restrict or stop driving," they conclude in the January issue of Investigative Ophthalmology & Visual Science.

There are 30 million US drivers older than 65, Keay and her team note, and these drivers show a "strong preference" for driving on their own rather than using public transportation. Driving helps them stay independent and involved in activities outside the home, the researchers add, but little is known about how older drivers make the decision to quit or restrict their driving.

To investigate, Keay and her team tested several aspects of visual and cognitive function in 1,202 licensed drivers 67 to 87 years old, and then surveyed them 1 year later about their driving habits. The study participants lived in a Maryland town with little access to public transportation.

One year after the study began, 1.5% of the study participants had stopped driving, while 3.4% had restricted their driving to their immediate neighborhoods. Women were four times as likely as men to have stopped or restricted their driving.

Certain aspects of visual and cognitive function were associated with the likelihood of quitting or restricting driving, the researchers found. Individuals who showed impaired visual scanning and psychomotor speed (the time it takes for a person to respond to a signal), assessed with timed tests requiring them to connect a series of numbered or lettered circles, were more likely to have put away their keys or limited their driving.

Low scores on a test requiring people to copy a series of increasingly complex figures, a gauge of a person's ability to coordinate their movements with visual stimuli, also predicted the likelihood of restricting or stopping driving, as did loss of contrast sensitivity, which is essential for driving at night and in bad weather.

Keay and her team also found that people with symptoms of depression were more likely to give up or restrict their driving, while people who expressed a preference for driving themselves at the study's outset were more likely to still be driving. The subjects' health and medication use were not factors that influenced whether or not they continued to drive.

"The decision to stop or limit driving to one's own neighborhood has major implications for personal independence -- but it is an important way to maintain the safety of older drivers and those who share the road," Keay notes in a press release accompanying the study. "As a society, we would like to think that when a driver recognizes that his or her functions related to vision or cognition are declining, they make that crucial decision. My colleagues and I found it reassuring that in this group, that appeared to be the case."

SOURCE: Investigative Ophthalmology & Visual Science, January 2009.

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