Young people, children more at risk from hot weather than older people

A new study has turned the conventional wisdom about the dangers of hot weather on its head, finding that young people in Mexico - not older people - are the most frequently dying from heat exposure.

The research found that 75 percent of heat-related deaths occur among people under 35, and many of the victims are healthy young adults.

Serious effects on young people

According to Study Finds, people under 35 account for 87 percent of heat-related life years lost.

“It’s a surprise. These are the most physiologically robust people in the population,” study co-author Jeffrey Schrader of Columbia University’s School of Climate Science said in a statement. “I’d like to know why that is.”

For decades, scientists and public health officials have focused their efforts on protecting older people from the heat, believing they are most vulnerable to extreme temperatures.

The Most Sensitive Group

But when the researchers analyzed death records in Mexico, they discovered something unexpected: Between 1998 and 2019, the country saw about 3,300 heat-related deaths each year, with nearly a third of them occurring among people ages 18 to 35.

Even more surprisingly, those ages 50 to 70, who were thought to be most at risk, actually had the lowest rates of heat-related deaths.

To understand this pattern, the researchers chose to study Mexico for a specific reason: The country keeps detailed records of both deaths and daily temperatures for each local area, creating a rich data set for analysis.

The researchers described this wealth of data as a massive weather and health diary covering an entire nation, with entries spanning more than two decades and including information on 13.4 million deaths.

The impact of heat and humidity

The researchers focused on what’s called the “wet-bulb temperature,” a measurement that combines heat and humidity to show how well our bodies cool themselves through sweating.

The researchers explained the source of the risk: On a dry, hot day, sweat evaporates quickly and helps cool the body. But on a humid day, even if it is not hot, the air is already so full of moisture that sweat cannot evaporate effectively, making it difficult for the body to cool itself by sweating.

Impact on young people and children

The high death rate among young people, especially those aged 18 to 34, is largely due to their working conditions.

"These are the younger people, who are at the bottom of the career ladder, and who probably do the lion's share of the hard work, with inflexible work arrangements," the researchers said.

Children under 5, especially infants, face different challenges

Young people are particularly vulnerable because of their physical structure: they have a higher ratio of surface area to body weight, which means they absorb heat faster than adults.

The ability of young people to sweat – the body's main cooling mechanism – is also not fully developed. In addition, their immune systems are still maturing, making them more susceptible to diseases common in hot, humid conditions, such as those spread by mosquitoes or contaminated water. While this study focused on Mexico, its implications extend far beyond its borders, with countries in Africa and Asia, particularly those that are agricultural or have limited access to air conditioning.