This summer, The duty takes you on the side roads of university life. A proposal that is both scholarly and intimate, to be picked up like a postcard. Today, we are interested in climate change and its effects on human health.
There is no longer any doubt that it is getting hotter and hotter on Earth, with the past eight years being the hottest on record. These climate changes pose several direct and indirect threats to human health. A direct consequence is the increase in the frequency, duration and intensity of periods of extreme heat, such as heat waves. Extreme heat carries health risks.
In 2003, a European heat wave killed 70,000 people. In 2021, the heat dome that hovered over the west coast of North America killed more than 600 people in British Columbia. In 2022, the hottest summer on record in Europe killed more than 60,000 people. Since periods of extreme heat will continue to intensify in the years to come, it is more important than ever to understand how heat affects our health in order to minimize the consequences.
Heat and health; a dangerous cocktail
The heat-related health risks stem from a three-ingredient cocktail. First, the internal body temperature rises, which can lead to heat exhaustion (dizziness, nausea) or, in the worst case, heat stroke, which is fatal if not recognized and treated immediately.
Second, sweating is our body’s primary way of cooling itself. However, sweating causes loss of body water and can therefore lead to dehydration if our fluid intake is insufficient. Dehydration increases the work of the kidneys, which can cause electrolyte imbalance and kidney failure.
Third, the heart works harder when exposed to heat to pump blood to the surface of the skin to promote heat loss to the environment. However, the work of the heart can overwhelm its ability to supply itself with oxygen and nutrients. In this case, cardiac events can occur, such as a heart attack, for example.
Who is predisposed to the health risks of heat?
While no one is immune to the health risks posed by heat, some people are more predisposed to it. Several factors, individual or related to the living environment, can modulate our sensitivity and act as risk factors. For example, age (young children and seniors), pre-existing health conditions, taking certain medications, being overweight and obese, low functional and cognitive abilities, and low physical capacity are all associated with a higher risk of hospitalization or death during an extreme heat event.
Among the factors related to the living environment, low socioeconomic status, limited access to cool or air-conditioned places, among others, also confer a higher risk. Finally, people who perform physical efforts during heat episodes (eg workers, athletes, law enforcement) are also at greater risk.
How to protect yourself from the heat?
The most effective strategy is simply to avoid exposure to heat, and the air conditioner is by far the most effective method of doing this. However, it is important to recognize that the air conditioner is inaccessible for many people, due to its high monetary and energy cost. Additionally, large-scale use of the air conditioner can overload the electrical grid, causing power outages, and it can contribute to greenhouse gas emissions if powered by non-renewable energy sources.
In recent years, several scientific studies have identified more sustainable and accessible cooling strategies. On an urban scale, the creation of fountains, green spaces, shaded areas, or even the reduction of road traffic would make it possible to increase society’s ability to adapt to heat.
On an individual level, strategies such as the fan, sprinkling water on the skin, immersing feet in cold water, using cold towels, ingesting cool water, decreasing physical activity, optimizing clothing, or a combination of these strategies can be used to reduce the effect of heat on our bodies.
Sweat to advance science
At the Human Integrative Physiology Laboratory of the ÉPIC Center of the Montreal Heart Institute, we are working to better understand how the human body reacts and adapts to heat. To do this, we invite volunteers to expose themselves to heat in the laboratory and we measure their physiological responses. We use several sources of heat, such as a climatic room which makes it possible to control the air temperature between –18°C and +70°C as well as the humidity level (dry or humid), hot water baths, specialized clothes containing tubing which allows the circulation of hot water and physical exercise.
We use these methods to study the ability of seniors to adapt to heat, to determine how heat predisposes to greater risk of cardiac events, to identify alternatives to air conditioning to reduce the effects of heat on people living with heart disease, to optimize worker health and safety in hot weather, and to predict individual factors that would predispose to greater health risk during periods of extreme heat.
Faced with an ever warmer future, our ultimate goal is to help our society adapt to rising global temperatures, enabling us to be better equipped to deal with heat-related health risks.