Many older Canadians are driving well beyond the time they should stop getting behind the wheel, according to the results of a new study that suggests a need for more mandatory testing.

A three-year study following more than 700 older drivers found close to one-third continued to drive after being diagnosed with mild to moderate forms of dementia, Dr. Nathan Herrmann, a professor of geriatric psychiatry at the University of Toronto, and his colleagues found.

Dr. Nathan Herrmann.
(CBC)

Half the patients with dementia were still driving about two years after their diagnosis, Herrmann's team reports in Tuesday's issue of the Canadian Medical Association Journal.

"The fact there was such a large number of individuals with well-diagnosed dementia that were still driving when we started the study, that was the biggest shock to me initially," said Herrmann.

Driving offers independence that is difficult to give up. But elderly drivers and those with dementia may show poor judgment on the road, such as making a left turn into oncoming traffic or going the wrong way on a freeway.

Allan Dobbs.
(CBC)

Motor vehicle accidents kill 3,000 Canadians each year. Research shows those with dementia can be as likely to cause a crash as an inexperienced 16-year-old or someone driving drunk.

Medical conditions that affect fitness to drive are the main reason for crashes in drivers over 75, according to a journal commentary accompanying the study.

Dementia can affect critical judgment, colour recognition (such as if a traffic light is red), and reaction time.

"Everybody who has progressive dementia will at one point or another have to stop driving," said Allan Dobbs, who runs driving assessment centres in 20 Canadian cities. "The question is when."

Currently, seven provinces have mandatory testing for drivers, which happens if a doctor or family member makes a complaint.

Gary Moorcroft, 57, of Brampton, Ont., is affected by Alzheimer's disease and is facing the difficult decision of when to give up driving. 

"I'm really nervous about the day we have to take his licence away for good," said his wife, Carol Moorcroft. "I just feel it will be taking away his independence."

Gary Moorcroft said that if he was told his licence needs to be taken away, he would "have to just live with it."

Behaviour changes

Herrmann's study concluded that the severity of dementia and advanced age are linked to driving cessation. The presence of hallucinations and apathy appeared to hasten retirement from driving, while agitation and aggression were linked with more advanced dementia.

"Perhaps families and physicians were reticent to confront people who display these symptoms, or perhaps these individuals tend to be resistive to the recommendation to cease driving," David Carr of the geriatrics department of Washington University in St. Louis said in a journal commentary.

The personality types of the driver and caregiver, need for a licensed driver in the household, prior level of driving activity and the proximity of other family members also relate to the decision not to drive, but were not examined in the study, the commentary said.

Physicians' guide

An upcoming edition of the CMA's Determining Medical Fitness to Drive — A Guide for Physicians will emphasize functional tests rather than relying exclusively on a diagnosis, said Dr. David Butcher, a family practitioner in Prince George, B.C.

Physicians need to weigh the ethics of reporting when a patient's medical condition could affect driving with the potential damage to the doctor-patient relationship.

"Driving restrictions may be perceived by the patient as unnecessary, even punitive," Butcher wrote.

The effect of multiple medical conditions such as diabetes or a heart condition combined with the effects of aging and slower reflexes could be partially offset by driving experience and a person's ability to compensate and all should be taken into account, Butcher said.