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:

• 470 deaths.
• 225 hospitalizations.
• 36,000 ER visits.
• 7,200 ambulance trips.
• 15,000 calls to the Info-santé health-care hotline.

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.

Different study, different result

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.

So who’s right?

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.

The INRS study had a much broader definition of heat.

“We were looking at the cumulative impact of every day of summer, so of course the impact will be higher,” Boudreault said.

“By having this more holistic look at heat, we can derive a more general portrait of its impact on health,” he said.

Another difference between the two studies was the time period examined.

While the Statistics Canada study looked at a 20-year average, most of the data in the IRNS study was more recent.

Quick noted there have been more extreme heat events in recent years as the effects of climate change have become more profound.

“[The year] 2000 looks a lot different than 2020, which might even look a lot different than what we’re experiencing right now,” Quick said. 

“We looked at 20 years as a whole, to provide a very high level sort of average picture of what’s going on in these large Canadian cities,” he said.

“I think when we’re trying to understand the links between heat and health, it’s important to have a lot of different perspectives,” Quick said.

Likely to get worse

Those different methodologies show how both studies can be accurate at the same time.

Boudreault said it’s up to governments to decide how to react to the results of the INRS study, but he said one idea might be to consider lowering the thresholds for what’s considered extreme heat.

That way people might be better prepared to stay cooler at all times from May to September, and not just during extreme heat events in summer.

Francis Martel, a spokesperson for Quebec’s Health Ministry, responded to CBC News in an email about the INRS study’s findings.

“The ministry is aware of the harmful effects of extreme heat on the health of the population and consequently, on the health system. With global warming, episodes of extreme heat are expected to increase,” Martel said.

He said several changes have been made in recent years to better protect seniors, who are among the most vulnerable to heat deaths, including:

• Cool refuge areas in all long-term care homes. 
• Air conditioning in 70 per cent of long-term care homes.
• Free individual air conditioner installation for residents of long-term care homes.
• Awareness campaigns regarding extreme heat.

Boudreault said the number of heat-related deaths and costs for the health-care system are likely to increase if the effects of climate change aren’t slowed down.

“When we look at the future over 50 years, we’ll see a major increase,” Boudreault said.

“It’s a hypothetical future if we do nothing. But of course we hope we’ll do something and take action to reduce this burden,” he said.