Older adults who have fallen are 40% more likely to crash their cars than those who have not fallen, according to a new review of 15 studies of driving behavior involving almost 47,000 older adults.

The research, conducted by a investigators at the University of Colorado and Columbia University, has been published online ahead of print by the Journal of the American Geriatrics Society.

Falls, or the factors that cause falls and crashes, accounted for more than 177,000 additional car crashes each year, the review found, based on estimates of car crashes involving older drivers and older adults who fall. And falls may be an independent factor impairing an older adult’s ability to drive safely, they said, suggesting that some motor vehicle crashes might be caused by the falls themselves, regardless of the driver’s underlying health and functioning.

To help avoid falls and car crashes and live as independently as possible, the researchers recommend, older adults should exercise to improve physical and mental well-being, undertake efforts to improve mental function and address vision problems — for instance, with cataract surgery. When adults do fall, the researchers recommend rehabilitation afterward to help improve functional ability.

Other new research, from Saarland University in Germany, suggests that older adults who drive may want to avoid using voice navigation systems in their cars.

Seventy participants helped the researchers study how seniors reacted to complicated language commands while driving; 36 were older adults with an average age of 72, and 34 were members of a control group with an average age of 23.

The researchers used sentences that would seem familiar to participants at first, but then took a surprising turn. The participants were given these sentences as well as simple statements, played through speakers, and then had to signal with a yes or no response whether the sentence was linguistically correct and made sense. At the same time, they had to “drive” along a street in a driving simulator. They were shown two vertical, colored bars, one of which was controlled by the computer. They were asked to control the second bar using the steering wheel, such that the distance between the two remained as small as possible.

“While the younger participants showed stable behavior with both simple and more complex statements, seniors directed their full attention to resolving the linguistic inconsistencies and neglected the control of the vehicle,” the researchers said. This effect was particularly clear for seniors with low cognitive control, they added.