Extreme heat is a silent killer.

From time to time we hear of shocking cases of football players and other sportsmen who die suddenly during physical exertion on hot days. Such deaths are certainly tragic, but statistically they are very rare.

Most deaths from extreme heat are among the elderly, who often die alone in their homes. They often die slowly as the heat rises to body temperature and sometimes even exceeds it, especially when heat domes build up over cities and the temperature remains high day and night. When such deaths happen, they rarely make the news.

Of all the climate disasters our world is already experiencing, heat is the leading cause of death, the World Meteorological Organization reported. From July 2023 to June 2024, the temperature on our planet was more than 1.5°C above the pre-industrial baseline for twelve consecutive months. In July of this year, we experienced the hottest three days on record, prompting UN Secretary-General Antonio Guterres to issue a special statement.

Health risks and heat

Our bodies are designed to release excess heat when we are too warm, but this process is reversed when the air is warmer than our core body temperature. Our other main defense, sweating, is no help when the air is saturated with moisture and our own moisture cannot evaporate.

For the frail and elderly, who are more likely to struggle with heart problems, COPD or other issues, just sitting still during a heatwave is an effort equivalent to walking on a treadmill. The effort is not great, but it is constant and relentless. It exhausts the body, sometimes to the point of no return.

Tracking heat-related deaths is challenging and changing as authorities become increasingly aware that heat is a contributing or underlying factor in deaths from other causes. A American Journal of Public Health points out that the 1995 Chicago heat wave probably resulted in hundreds more deaths than were initially attributed to the heat itself.

Who is at risk?

Many people do not have air conditioning or cannot get to places where it does exist, such as a library, leisure centre or shopping centre. As a result, too many people in cities are forced to endure long heat waves – waves that are occurring more frequently, lasting longer and reaching higher temperatures – and this trend appears to be getting worse.

Air conditioning, once a luxury that lured people to the movies on hot summer nights, has become a necessity. It is also increasingly required by law: cities are passing ordinances requiring landlords to keep the temperature in their tenants’ apartments from rising above a certain level. In Toronto, there is such an ordinance for rental apartments with air conditioning that limits the indoor temperature to 26 degrees Celsius between June 2 and September 14.

Such laws take into account the vulnerability of tenants who have no control over the temperature in their rental apartments, making heat deaths a particularly tragic urban phenomenon, as confirmed by a recent study by Statistics Canada between 2000 and 2020. Deaths from extreme heat were more likely to occur in cities with a higher proportion of renter households.

During a single week-long heat wave in June 2021 – a year after the period covered by Statistics Canada’s study – British Columbia’s chief coroner found that 570 people died from heat-related causes – 79 percent of them seniors.

Measures at community level

From the Global North perspective, the following community members are most likely to die from extreme heat:

• People over 65
• People with multiple chronic diseases (including high blood pressure, mental illness, diabetes, heart disease, lung disease)
• Socially disadvantaged population groups in our communities
• People with reduced mobility
• People who experience social isolation (living alone)
• Tenants with no air conditioning
• Those who live in an urban heat island

This problem will not go away.

Actions we can take to protect the most vulnerable members of our community include:

• Raise awareness that excessive heat is not only unpleasant but also dangerous.
• Ensure that the population is warned of impending heat waves.
• Work to ensure that everyone has access to air conditioning.
• Check on people who live alone and support them, especially if they do not have air conditioning.
• Invite people over if you have air conditioning or help them get to local cooling stations.
• Help vulnerable people who don’t have air conditioning to improvise, for example by freezing wet towels, taking them out and hanging them around their necks. This can be surprisingly effective, especially if a fan is running.
• Learn the warning signs of heat-related illnesses and pass them on.
• Make sure your child drinks plenty of water and other nutritional fluids.

While we must do our best to curb climate change and prevent our planet from warming even more, we must also make every effort to protect vulnerable people from the effects of the heat that already exists.

Myles David Sergeant, Assistant Professor of Clinical Medicine, Department of Family Medicine, McMaster University

This article is republished from The Conversation under a Creative Commons license. Read the original article.