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'Even young people die in the heat': The stages of heat stroke

B.C. has recorded nearly 500 sudden deaths since the heat wave began.
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B.C.'s heat wave has had devastating consequences, including nearly 500 sudden deaths.

A record-breaking heat wave that enveloped British Columbia over the last five days is believed to be linked to hundreds of deaths and counting. 

The BC Coroners Service said Wednesday it has tallied 486 deaths across the province from Friday to Tuesday.  

That’s above and beyond the province’s baseline. Over a normal five-day period, B.C.'s Chief Coroner Lisa Lapointe said 165 people die a sudden death. Many of the dead coroners are finding are those who live alone in unventilated homes. 

But it’s not just old or infirm that are hit by heat death.

“Even young people die in the heat: football players, long-distance runners,” said the BC Centre for Disease Control’s Dr. Tom Kosatsky, who as medical director of environmental health, is in charge of everything from health inspectors and food safety to the knock-on effects of climate change. As he puts it, “Everything the environment can do to hurt you.”

Heat is on his radar. It’s already the number one cause of weather-related death in the United States. In Canada, where climate change is warming some areas up to four times faster than the global average, many are just coming to grips with its deadly potential.

“This, frankly, took many of us off guard,” said Lapointe Wednesday. “I think it’s very likely many of us misunderstood the extreme risk.” 

What does too much heat do to the human body? In a word: hyperthermia.


Death by heat starts slow. Too much time under the sun or stuck in a hot apartment has made you tired, and at times, dizzy. 

If you are an outdoor worker — a firefighter, a baker, a farmer or a construction worker — you face bigger risks when heat waves hit. Genetics matter less than age and the ability to get out of a wheelchair or bed, Kosatsky explained.

Those over 65, who are overweight or have pre-existing medical conditions, like heart disease or high blood pressure, tend to have a harder time avoiding the worst heat illnesses, he said.

Medication, such as diuretics, or recreational drugs like cocaine and amphetamines can interfere with your body’s ability to compensate for the heat. Alcohol only accelerates dehydration. Alone under punishing heat and with little water, those factors set the stage for a devastating spiral. 

Heat stress

As you begin the march toward hyperthermia, you might have a headache, feel tired or dizzy.

When heat stress hits you, you know you’re thirsty. You need water.

Heat fatigue

Your palms sweat. You don’t want to do anything. 

You got too much sun — a heat rash has flared up in your armpits and elbow creases.

Or maybe you forgot to put on sunscreen at the beach. You are burned. 

But it’s nothing you haven’t dealt with before.

Heat cramps

The mercury rises, your dehydration deepens. Painful muscle spasms come and go due to a lack of electrolytes.

All that sweating has depleted your body of vital minerals like potassium, sodium and calcium — Gatorade, basically — that help fire the chemical reactions in your muscles. 

Anyone working hard in hot conditions is especially vulnerable, and heat cramps are known to hit hikers and people working under the sun.

“It can occur anytime you’re dehydrated,” said Kosatsky. “But it’s much more likely to occur in the heat.” 

At this point, finding a cool place and restoring fluid with electrolytes can bring a person back. But if you’re stuck in an apartment or caught under the sun, things can turn quickly.

“People can go one way or another,” said Kosatsky.

Heat syncope

The other way? Heat syncope. 

You speak in broken words, unable to string together full thoughts.

A lack of water has reduced the volume of blood in your body. As the blood thickens, your body fights to keep your temperature down by pushing blood to the skin to induce sweating. 

An adult can lose a litre of water an hour this way; if they don’t drink more, the blood continues to thicken in a vicious cycle, drawing blood from the brain and sending your head spinning in dizziness. 

You faint.

Heat exhaustion 

Your heart, your body’s biological pump, is pounding to drive blood toward the skin — to sweat. 

You have a fever. You’re irritable. Sweat pours out of your body as it works to stay in the range where human life is possible. Dizziness has escalated to disorientation. You are confused, can’t see straight and want to vomit.

You need cold compresses, an ice-cold shower or a jump in the lake to regulate your body temperature. You need water.

“Paradoxically, they deny thirst, they get so far along they don’t feel thirsty anymore,” said Kosatsky.

Heat stroke

Your sweat runs dry, spiking your fever to over 41 C.

Your body wants to move into damage control, it wants to move blood to the organs keeping you alive. But without enough of it to go around, your blood pressure plummets, the vital fluid now a thick sludge. 

As blood retreats from your organs, blood vessels begin to collapse. 

You start to hallucinate. 

Then your organs shut down — maybe the kidneys first. 

The mud-thick blood now clogs in your blood vessels, perhaps triggering a stroke.

Your heart fails.

“That’s lethal,” said Kosatsky.


Dying of heat is never a straight line. Medical experts usually pay attention to heat cramps, heat exhaustion and heat stroke. 

“There’s a trigger temperature,” said Michael Brauer, a researcher who studies the health effects of extreme heat at the UBC’s School of Population and Public Health.

“Once you get beyond that, things can go up after that exponentially.”

Experts say there’s a three- to four-day documented lag time between death and a heat wave’s peak. 

“The worst is not over,” said Armel Castellan, a warning preparedness meteorologist with Environment Canada.

The worst is also hard to measure. Deaths are expected to rise beyond the tragic cases of seniors left alone in an apartment without air conditioning. 

Brauer said researchers have documented spikes in everything from suicides and homicides to workplace accidents and drownings as more people flock to the water. 

Most of those haven’t been traditionally tallied by agencies like the BC Coroners Service, which relies on a medical model to determine the cause of death. The heat wave and the decades of anthropogenic climate change that “definitely has its fingerprints on this event,” according to Castellan, don’t appear on the death certificate.

“We know every year in the world, there are like four million deaths linked to air pollution,” said Brauer, 

“It’s the same issue here. You can just hear the sirens at night. There are a lot of people dying. This is due to the heat. But we just don’t put that on death certificates.” 

In the same way a Royal Society of Canada task force recently found evidence that roughly 6,000 COVID-19 deaths “may have been missed” across Canada, it will likely take months of research to determine just how many people died because of heat.

Whatever the results of the BC Coroners Service investigation, Brauer said he hopes this heat wave will reinforce for British Columbians just how deadly heat can be.

“We’ve been saying this. We’ve known this for decades,” he said. “The depressing thing is the train has already left the station.... It’s now about adaptation. So that in the next heat event, how do we avoid what we’re seeing now?”

Stefan Labbé is a solutions journalist. That means he covers how people are responding to problems linked to climate change — from housing to energy and everything in between. Have a story idea? Get in touch. Email [email protected].