Study suggests hundreds of Quebec deaths each year are related to heat

A new study from Quebec's Institut national de la recherche scientifique (INRS) suggests that heat is responsible for 470 deaths per year in the province, and that the number will increase if nothing changes.

The study looked at the impact of heat throughout the health-care system and found that each year in Quebec, heat is linked to:

Previous studies have looked mostly at the impact of specific periods of extreme heat — heat waves — such as the one bombarding much of Quebec right now.

This study, the first of its kind in the province, used statistical models to estimate total deaths and impacts caused by hot weather throughout the summer.

Researchers looked not only at data from heat waves, but from all days with warm temperatures from May to September.

"It's a different view, but for us it's a more comprehensive view of the burden of heat," the study's lead author, Jérémie Boudreault, told CBC News in an interview Tuesday.

"It was kind of surprising. In the end there's no part of our health system that's not impacted by heat," Boudreault said.

Coincidentally, another study also released Tuesday looking at heat-related deaths — this one from Statistics Canada — came up with a much lower estimate.

The study looked at data from 2000 to 2020 from the 12 most populous cities in Canada, including Montreal.

"We found that during this 20-year period approximately 300 excess deaths occurred in Montreal during extreme heat events," Matthew Quick, a research analyst at Statistics Canada, told CBC News in an interview Tuesday.

If you break down the data from the INRS study and isolate Montreal, it estimates 180 heat-related deaths a year for the city. Over a 20-year period that would be 3,600 deaths — more than 10 times what Statistics Canada found.

What accounts for the different results?

The Statistics Canada study looked only at deaths related to extreme heat events as defined by cities. Those definitions can vary from city to city. 

In Montreal, an extreme heat event is defined as three or more consecutive days where the minimum temperature is greater than 22 C and maximum temperature is greater than 30 C.