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Driving and dementia: a messy issue

Accepting a diagnosis of dementia is difficult enough. But for some people the prospect of giving up their driver's licence, and the independence it represents, is the hardest part.

While having mild dementia doesn't necessarily mean you are unfit to drive, the statistics show how important it is to make the right call. Older adults with mild dementia have eight times the crash risk compared to those with normal cognitive function. They also have a 50 per cent risk of a serious crash within two years of diagnosis.

The difficulty is that those with dementia often don’t realize their driving has deteriorated, and doctors don't have objective tools to assess their fitness. Even so, in some provinces, doctors must report patients whom they feel can no longer safely drive. 

It is also important to consider contacting the car insurance provider to share any information received from the doctor, as there may be changes to coverage based on the specific situation. Failure to disclose a diagnosis could impact the insurance policy.

Tom_Schweizer

"It's a messy issue," says Dr. Tom Schweizer, a neuroscientist at Toronto's St. Michael's Hospital. "Assessment is an ambiguous, subjective, patient by patient process."

Doctors can order tests to assess executive function, visual-spatial abilities, short-term memory and reaction time. Together, these tests give a broad picture of cognitive abilities and can help make a diagnosis of dementia, but not of fitness to drive.

However, if these tests show moderate to severe dementia, Canadian Medical Association (CMA) guidelines are unequivocal: notify the ministry. Motorists can then contest their doctor's assessment by paying $500 to $800 for an on-road test — considered the gold standard driving assessment.

But it's when motorists have mild dementia that things get murky. The CMA guidelines have nothing to say about when a finding of mild dementia should lead to a call to the ministry. It is at best a guessing game.

Dr. Schweizer aims to change that. He and his team at St. Michael's Hospital are in the midst of a two-year study to better understand what types of driving impairments affect people with dementia and what brain regions are at play.

With funding from the Alzheimer Society Research Program, they are scanning the brains of three groups of 15 drivers as they use a driving simulator. One group has no health issues, the second group has a diagnosis of mild cognitive impairment and the third a diagnosis of early-stage Alzheimer's.

Watching drivers' brains in action

What makes this study unique is that it uses a highly-realistic driving simulator inside an MRI scanning machine. This means the researchers can see what is happening in participants' brain as they attempt all the manoeuvres necessary for safe driving.

"The simulator comes complete with an accelerator, brake and steering wheel," says Dr. Schweizer. "It's as realistic as it gets without being in a car."

Most accidents happen during left turns at busy intersections, so he and his team expect the groups with mild cognitive impairment and early-stage Alzheimer's will have trouble with this manoeuvre.

And since the frontal lobe is associated with the ability to pay attention and plan for such actions, it is likely this brain region will show less activity in these two groups.

High costs and backlogs means it's not possible to use MRIs to assess driving abilities. But once Dr. Schweizer and his team have identified the brain regions important for driving, they can develop behavioural tests that pinpoint problems with these regions.

Doctors will then be able to administer these tests with the confidence that they provide a robust and accurate assessment of patients' ability to drive safely.

"As the population ages, we know the number of drivers with dementia is going up. The boom is coming," says Dr. Schweizer. "We need well-defined tests that correlate with driving ability."

Do you want better care for people with dementia and to help find a cure? The Alzheimer Society Research Program seeks to fund the most promising research. Whatever you donate today will help us reach our goal faster.


Last Updated: 05/03/16
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