Extreme heat deaths higher among seniors and in cities with more renters, study says

TORONTO — Deaths in Canada's 12 most populous cities go up during extreme heat waves and people aged 65 and older are at higher risk than those who are younger, says a Statistics Canada report released Wednesday.

The cities examined were: Brampton, Ont.; Calgary; Edmonton; Hamilton; Mississauga, Ont.; Montreal; Ottawa; Quebec; Surrey, B.C.; Toronto; Vancouver and Winnipeg.

Cities with larger proportions of renters had higher risks of death during extreme heat waves.

That's in line with previous research that suggests people who rent are less likely to have air conditioning than people who own their homes, StatCan research analyst Matthew Quick said in an interview.

That elevated risk could also signal an equity issue, said Dr. Anna Gunz, an associate professor of medicine at Western University in London, Ont.

"Are rental properties also places where there might be a little bit of a green desert and people aren't living close to trees and parks and other pieces of green space that we also know can ambiently cool the area?" said Gunz, who specializes in climate change and heat.

The study looked at daily mortality data for two decades between 2000 and 2020 and also found that the risk of heat-related deaths was higher in cities where extreme heat was less common, including Vancouver and Surrey.

Although the data can't show cause, one possible explanation could be that those cities have fewer adaptation measures, such as air conditioning, than other cities, Quick said.

"(Or) maybe people are more aware of the impacts of extreme heat and adjust their daily routines accordingly," he said of people in places that see more extreme heat.

The study looked at respiratory, cardiovascular and "non-accidental" deaths during heat waves. "Non-accidental" is a non-specific category that includes deaths that weren't caused by accidents such as car crashes or poisonings, Quick said.

Seniors in both Montreal and Toronto had higher rates of deaths due to respiratory causes on extremely hot days, according to the data.

People age 65 and older in Montreal also had higher risk of cardiovascular deaths during extreme heat waves.

"It's well known in the scientific literature that high temperatures, extreme heat is associated with higher risks of death, more hospitalizations, more emergency calls, these types of health outcomes," Quick said.

But past research looked at deaths after specific extreme heat events and this study took a broader approach, he said.

"What this study aimed to do was to be very high-level, to look across a range of different cities and climates in Canada and try and understand the average impact over 21 years."

This report by The Canadian Press was first published June 19, 2024.

Canadian Press health coverage receives support through a partnership with the Canadian Medical Association. CP is solely responsible for this content.

Nicole Ireland, The Canadian Press