Warnings to at-risk drivers reduce vehicle crashes

A system where doctors routinely reported drivers who might be impaired by chronic illness cut the risk of car crashes by 45 percent in a new study from Ontario, Canada.

That includes people with alcoholism, epilepsy or uncontrolled high blood pressure, researchers said.

But one downside, the study found, is that people were less likely to go back to doctors who had given them a medical warning and reported it to the government.

Nonetheless, lead researcher Dr. Donald Redelmeier of the Sunnybrook Health Sciences Centre in Toronto told Reuters Health the findings should convince doctors to warn patients about driving risks.

"It isn't just that it can save your patient's life, not just that (not reporting) imposes risks on others in the community as well," he said. "It's also that crashes are such a widespread cause of property damage that everybody pays, either through insurance premiums, or congested roadways, or the price of consumer goods."

If the results from the Canadian study, conducted by the Institute for Clinical Evaluative Sciences, were extrapolated throughout the United States, he said the annual savings might total $160 million.

Smaller studies have offered conflicting findings about the effectiveness of such warnings.

The new report, published in The New England Journal of Medicine, looked at the risk of getting in a crash and needing emergency room care in 100,075 people who were advised by their doctor not to drive.

Since 2006, doctors in Ontario have been paid $36.25 per case to encourage reporting of such problems. Patients subsequently receive a warning letter from the government.

The reasons for getting a warning letter in this study ranged from diagnoses of uncontrolled high blood pressure and diabetes to epilepsy and stroke.

"The vast majority of patients in our study had more than one of those disorders," said Redelmeier - including 21 percent who had five or more conditions on the worrisome-driving list.

Among the people reported under the program, 10 to 30 percent ultimately had their license suspended, "so everybody gets cautioned, but relatively few people get suspended," he said.

AN ‘IMMEDIATE, SUBSTANTIAL' EFFECT

During the three years prior to the warning, 1 in 210 people in the study were involved in a crash that resulted in an ER trip each year - about double the rate in the general population.

One year after the warning was issued, the risk to those patients had fallen to 1 in 367, a 45-percent reduction.

"The reduction in risk was immediate, substantial, and sustained," the researchers said. "Together, these data suggest that warning patients who are medically unfit to drive may reduce the risk of road crashes."