Why do Alzheimerâ€™s patients wander?

A Toronto-area family is grieving after an 83-year-old woman with Alzheimer's disease was struck and killed on Highway 400 early Thursday morning after wandering away from home — and at least one expert is concerned this could happen more often given the aging population.

About 200,000 people in Ontario are living with dementia, and more than half of them will go missing at some point, according to the Alzheimer's Society of Canada.

Many wander because they are looking for stimulation, according to Dr. Tiffany Chow, a senior clinician-scientist at the Ross Memory Clinic at Baycrest Health Sciences in Toronto.

"They're unable to do the usual activities that kept them interested and engaged all their lives. And they're just out there, looking for something," Chow said Friday on CBC's Metro Morning.

Patients also often go "back in time," she said.

"They think they're late for work or think they're late picking the kids up, and they're trying to resolve that any way they can. But they can't access the car or don't have car keys, so they get there on foot.

"They're on a mission. It may be a misguided mission, but sometimes there's a reason," Chow said.

Confused seniors are usually found and returned by police, taxi drivers or even helpful strangers.

But families are encouraged to take preventive measures such as setting alarms or locking doors, provided someone is on the scene to unlock them in the event of a fire or other emergency. Alarms are also available that will go off if the person gets out of bed.

Caregivers can also make use of items that will identify and, in some cases, track the location of the patient. Bracelets that emit unique radio signals are available through the organization Project Lifesaver.

The Alzheimer's Society recommends caregivers register their loved ones with the Finding Your Way program, which provides police with essential information and a photo of the person who's wandered off.

In the Highway 400 incident in the Toronto area Thursday, the body of Chandrowci Basdeo, who was in the early stages of Alzheimer's, was found on the road, close to a service station, amid some broken parts of a vehicle. A man has been charged with failing to remain at the scene.

Const. Robyn Kassam, who specializes in seniors' safety for the York Regional Police, says the problem of wandering dementia patients could worsen.

"We're going to see in a few short years more seniors than children," Kassam told CBC News. "Does that mean we're going to be getting more calls for service, more missing persons calls? Quite possibly."