New test predicts crash risk of older drivers
A new vision test may ultimately help the elderly, their families, and physicians decide when it's okay for an older person to continue driving or when it may be time to hang up the car keys. Using a novel "useful field of view" test to measure how drivers process visual information, researchers at the University of Alabama at Birmingham (UAB) found that poor performance on the test was linked to an increased risk of car crashes. Drivers who showed a 40 percent or greater impairment in their useful field of view were more than twice as likely to be involved in a crash within 3 years of testing.
The research, by Cynthia Owsley, Ph.D., Karlene Ball, Ph.D., and colleagues from UAB and Western Kentucky University in Bowling Green, is reported in the April 8, 1998, issue of the Journal of the American Medical Association (JAMA) . The study was funded by the National Institute on Aging (NIA).
It is well known that older drivers are at greater risk of crashes or injury when compared to most other age groups. But there are large differences in their skills and abilities. The useful field of view test -- and maintaining or improving driving skills through visual attention training programs -- may be one way to address those differences and stay away from age-based restrictions on driving, the scientists say. "By measuring the skills directly related to driving, we can identify specific drivers who are at greatest risk," says Owsley. "Setting an arbitrary age limit for driving unjustifiably restricts the mobility and independence of older people. We're trying to help avoid that."
The study marks the first time that scientists have attempted to find out whether or not a visual processing test can predict the likelihood of future crashes for individual older adults. The test differs substantially from standard eye exams, which measure acuity or visual function, or the ability to see an object at a given distance. To assess their visual processing abilities, participants in this study looked at a computer screen with figures of cars, trucks, and other objects. The drivers were asked to identify a particular object amid different kinds of visual distractions on the screen. The useful field of view was defined as the area in which all of this rapidly presented visual information can be used. People who had measured difficulty with the task were considered to have an impaired useful field of view.
Some 294 drivers ranging in age from 55 to 87 participated in the study. In addition to being tested for visual function, information was collected on the participants' general health, mental status, and how often they drove so that the researchers could determine the factors involved in crashes over the 3-year follow-up period from 1990 to 1993. Crash reports involving the participants were collected from a state agency, and researchers compared the useful field of view scores and results from the other types of vision tests with the crash information. During the 3-year follow-up, 56 of the study's drivers were involved in at least one crash.
Performance on the useful field of view test was found to be directly related to involvement in a crash. People with a 40 percent or greater impairment in their useful field of view were more than twice as likely to be involved in a crash. For every 10 points of reduction in a driver's useful field of view measure, his or her crash risk rose by 16 percent, regardless of age. Other vision tests did not predict the risk of future crashes.
This study is very important for older people, their families, and their neighbors, says Jared B. Jobe, Ph.D., chief of the NIA's adult psychological development branch. Older drivers are involved in more crashes and fatalities per mile driven than most other age groups and are more likely to become disabled or die as a result of collisions than younger adults.
"This research shows there may be a way to protect older drivers and the community in a very reasonable way," Jobe states. More research is needed to make this type of testing practical and proven enough for doctors' offices and state licensing agencies. This study, however, goes a long way in demonstrating what may work, he says. Jobe noted that the NIA is funding additional work by Ball, Owsley and their colleagues to see if elements of the useful field of view test may be incorporated into training programs for older people to help those with a reduction in their useful field of view improve their driving skills.
Owsley's research is part of the NIA-sponsored Edward R. Roybal Centers for Research on Applied Gerontology, which were established to help move promising research findings out of the laboratory and into programs that can directly improve the lives of older people and their families.
Note: Two co-authors of the JAMA article, Karlene Ball, Ph.D., and Daniel L. Roenker, Ph.D., own stock in Visual Resources, Inc., the company that holds the patent to the useful field of view visual attention analyzer used in this study.
NIA, part of the National Institutes of Health, leads the national effort in research on aging, supporting and conducting basic, clinical, epidemiological, and behavioral and social research.