As Europe’s record warm weather winds down, the extent of its deadly toll is beginning to emerge.
Heat waves are a subtle disaster. People are not swept away or caught in the flames.
“I think of them as a creeping killer,” said Lucinda Coates, senior research scientist at Risk Frontiers.
“You can’t take a picture of them to illustrate a media story, they’re not dramatic.”
But their tranquility belies the horrific number of lives they claim.
Heatwaves are Australia’s deadliest natural disasters.
So how does the body respond to heat and what can we do to protect ourselves from extremely hot weather?
What happens to our body in extreme temperatures?
According to Ollie Jay, professor of heat and health at the University of Sydney and head of the Heat and Health Research Incubator, there are three main pathways that can lead to death when humans are exposed to extreme heat.
Be warned, they’re all pretty nasty.
Sweating is one of the ways the body tries to cool itself back down during times of extreme heat. (Provided: Unsplash)
1. A critically high core temperature
One of the ways the body responds to increased core temperature is by sending blood to the skin to help cool it.
Dr. Jay says it’s “a thermoregulatory response called vasodilation.”
But the body only has so much blood, so this reduces the amount of blood available to internal organs and, consequently, the amount of oxygen that gets to them.
This in turn reduces the stress on the bonds in the cells of the intestine.
“So you start to get something called ‘increased intestinal permeability,’ which means that all the nasty stuff that normally stays in your gut starts to leak out of your gut and into your circulation.” , explains Dr. Jay.
This causes a sepsis response, massive clotting around the body and can cause death.
2. Catastrophic cardiovascular event
“Again, we only have so much blood in the body,” notes Dr. Jay.
“If you redirect a lot of blood directly to the skin, to maintain blood pressure, your heart has to start working harder.”
There are many barriers that could prevent an effective behavioral response to extreme heat. (AP Photo: Matt Dunham)
The heart rate increases as the body tries to circulate a fixed amount of blood throughout the body at a faster rate.
“So if you have underlying heart muscle disease because you have cardiovascular disease, for example, you’re more likely to have a catastrophic cardiovascular event when you’re exposed to heat,” Dr. Jay said. he says
3. Dehydration and renal failure
The main way our body tries to cool off is by sweating, but again the body only has limited resources. If we don’t or can’t top up the tank, we will gradually dehydrate.
Dr. Jay warns “if you have an underlying kidney problem…say kidney disease or chronic kidney disease, that could lead to catastrophic kidney collapse or kidney failure.”
It’s not just heatstroke.
Heat waves are a much bigger risk in Australia, but the cold can kill you too. (ABC News Video)
A side note to all those shivering in South Australia right now: the cold can kill you too.
The key way your body fights the cold is by drawing blood to the core and shivering.
“So if we’re deprived of energy for whatever reason, if you’re stuck in the mountains, you’ve run out of food, then it becomes problematic,” says Dr. Jay.
“And if you’re deprived of oxygen, that’s a problem, too, because we need extra oxygen to fuel those muscle contractions through shivering.”
If your temperature drops low enough, you can become hypothermic, which can lead to death.
How deadly are heat waves?
Given that these heat-related deaths often present as other conditions, it can be tricky to determine precisely how many people die as a result of a heat wave.
“Heat-related deaths, or heat-related deaths, are generally not well documented,” according to Lucinda Coates.
Ms. Coates has spent many years studying heat wave deaths. He says the best way to tell if a person has died from the heat is to evaluate coronial records.
But even in coronial records, heat-related deaths can usually only be identified through a combination of an autopsy, plus an understanding of the circumstances surrounding the death.
“When a first responder arrives at a residence where a person has died, they may not be thinking about heat as a potential cause of death,” Ms Coates said.
“What that means is that many deaths that are in fact heat-related will not necessarily be recorded as such.”
An alternative method is to calculate excess deaths during the heat wave period compared to a similar period without the heat wave.
“For example, the 2009 heatwave, there were 374 excess deaths recorded for Victoria,” Ms Coates said.
A man cools off in a fountain during the hot weather in London last week. (Reuters: John Sibley)
“But the number of dead people who were actually recorded in the coronial registers for this time period is much lower.”
The problem with using excess deaths is that it involves a high degree of uncertainty; it is difficult to determine who and how many people died in a heat wave.
“It’s a very sad thing to study. But I guess what’s satisfying about all of this is that before we did the study, people didn’t really know that heat waves were a problem,” Ms Coates said.
“Now we do; now we’re doing things about it.”
What can we do to cool down?
How we handle heat depends on both our physiology and our behavior.
On the eve of a heat wave, there’s not much you can do to improve your physiology, but you can definitely change your behavior.
Nicole Vargas, Professor of Exercise Physiology at the Australian National University School of Medicine, is an expert on our behavior and hot flashes.
Behavioral responses to heat include things like drinking enough water, reducing physical activity, and seeking shade.
Strategies that cool the person instead of the entire room are effective and more sustainable for the planet. (Provided by Ollie Jay)
“Whether to drink cold or thermoneutral water or not [unchilled or around air temperature] water needs to be debated,” Vargas said.
“There is data showing that thermoneutral water may be better for maintaining hydration.
“It doesn’t feel that nice, but when you drink cold water, you feel like you’re drinking enough.
“But you don’t drink as much as when you’re drinking water at normal temperature.”
These behavioral responses depend on our ability to feel that we must respond.
“So if vulnerable people have problems with their thermal sensory signals, we could see that they are at greater risk of not engaging in certain behaviors,” Dr. Vargas said.
Even the most stoic need to stay hydrated in times of extreme heat. (AP Photo: Matt Dunham)
This is an ongoing area of research, but Dr. Vargas says there is some evidence to suggest that older people have a reduced sense of thirst, which may inhibit their behavioral response.
Another obstacle to responding effectively is socioeconomic disadvantage.
The work done by Ms. Coates has shown examples of people dying in their homes, where the air conditioner has not been turned on.
But Dr Jay, whose work in this area has been published in the journal The Lancet, says there are cost-effective measures people can implement to combat the heat, such as turning on the tap, submerging their feet , the use of wet clothes, the use of evaporative coolers, fogging. fans, electric fans, ice towels and drinking water.
The full infographic produced by Dr Jay and his team is publicly available. (Provided by Ollie Jay)
A word of warning though about electric fans; they are only useful up to a point where the air is very dry.
Without enough moisture around it gets to the point where it’s so hot that moving air doesn’t help cool you anymore.
“Ultimately, it’s like putting yourself in an oven and just blowing hot air,” says Dr. Vargas.
It doesn’t get better anytime soon
Beyond what we are doing on a personal level, governments could do more to reduce climate change.
Yuming Guo, Professor of Global Environmental Health and Head of Monash Climate, Air Quality Research Unit, says policies need to be developed to mitigate long-term changes in temperatures and weather patterns.
“They need to make policies to reduce carbon emissions from industry and other sources,” he says.
“Several studies, including those from my group, have clearly provided strong evidence that extremely high temperatures, including heat waves, and air pollution, including wildfire smoke, can increase mortality and morbidity risks “.
A 2021 study in Nature Climate Change found that about a third of heat-related deaths in the warm season could be attributed to anthropogenic climate change.
“If no urgent climate action is implemented, I have no doubt that there will be more and more terrible heat waves in the future,” says Dr Guo.