However, patients with added impairments, such as difficulty with multi-tasking or making quick decisions, are particularly likely to have trouble with tasks like staying in lanes and making left turns in traffic, the researchers write.
"Driving is a highly complex task that requires the integration of multiple cognitive functions, such as attention, memory, and visuospatial ability, all of which can be affected by mild cognitive impairment," said senior author Tom Schweizer, director of the neuroscience research program at St. Michael`s Hospital in Toronto.
"Despite this, there are no validated tools or guidelines to help assess the driving safety of patients with mild cognitive impairment," Schweizer told Reuters Health by email.
To study how mild cognitive impairment affects driving ability, Schweizer and colleagues recruited 24 patients with memory loss. They divided participants into two groups: one group with only memory problems, and another group with other cognitive problems too, such as issues with attention, reasoning/planning, or visual perception.
Twenty cognitively healthy participants in the same age range acted as a comparison group.
The participants underwent cognitive testing as well as a driving simulation that tested their ability to perform a range of tasks such as driving straight, making turns, and making left turns with oncoming traffic.
Overall, patients with mild cognitive impairment committed more than twice as many driving errors as the cognitively healthy drivers.
Memory impaired patients were more likely to cross the center line of the road and stray out of the legal driving lane than healthy drivers.
They were also more likely to make mistakes turning left with oncoming traffic, but they had no issues with turning right, or turning left with no traffic.
When researchers analyzed data on the two groups separately, however, they found that seniors with only memory issues were not more likely than healthy drivers to make errors.
Patients with multiple cognitive impairments, however, were at much greater risk of errors, including crossing the center line, missing stop signs, and straying out of the driving lane. These individuals were also much more likely to make errors during left turns.
A diagnosis of mild cognitive impairment alone "does not mean that someone should stop driving, but it is important to monitor for declines," said Jennifer Davis, a clinical neuropsychologist at Rhode Island Hospital who studies cognitive issues and driving.
Mild impairment is often a symptom of Alzheimer`s disease and is likely to get worse over time, "so it is also important to help patients and families identify when it might be time to stop driving," Davis, who was not involved in the study, noted by email.
"Families are encouraged to monitor driving by riding with their family member as a passenger," Davis advised, adding, "If concerns arise, be sure to see your doctor and consider taking a formal road test."
"These results highlight the importance of physicians talking to their patients about driving, even when cognitive deficits are very mild in nature," said Schweizer.
New tools are needed to help doctors better assess driving, he added.
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