Extreme heat fueled by the climate crisis is often viewed as primarily a problem for vulnerable segments of the population, such as elderly people. But it is people aged under 35 that are set to suffer the brunt of heat-related deaths as temperatures climb, new research has suggested.
While older people are susceptible to heatwaves, they currently make up the bulk of cold-related deaths. As the world heats up, it will be younger people that will suffer disproportionately as the mortality burden shifts, with the new study estimating a 32% increase in deaths of people under 35 years old this century from heat if greenhouse gases emissions aren’t radically cut.
“Most discussion of vulnerability to heat focuses on the elderly, but we found a surprising source of inequality in that most heat mortality is in younger people,” said Andrew Wilson, a Columbia University researcher who led the study, published in Science Advances, with a group of nine other scientists. “We didn’t think we’d find this.”
The study is based on data drawn from deaths in Mexico, a country of extensive mortality records and high “wet bulb” temperatures, which is a measurement that factors in humidity to ascertain the heat stress level upon people.
The researchers found that in the two decades until 2019, 75% of deaths from heat occurred among people younger than 35 while, conversely, almost all cold-related deaths were of those older than 50.
As most temperature-related deaths in Mexico, like in most countries, currently occur due to cold weather, the growing problem of extreme heat is likely to tip the balance towards more younger people dying, the research suggests. This pattern may well be replicated in other countries such as the US and in Europe, Wilson said, due to fundamental similarities in how different age groups react to temperature.
“We are seeing that cold-related deaths will fall, primarily of older individuals, while heat deaths of younger individuals will increase,” he added. “Climate change is here and how we adapt to it will be a very important determinant of human health in the future. We shouldn’t move resources away from older people but we certainly need to think more about the risk faced by younger people.”
There is no single answer as to why there is heightened risk for younger people but researchers said there are likely a number of factors, such as physiological differences – for example, babies are unable to sweat to release heat and are dependent upon caregivers – as well as occupational risks, such as a working age population that toils outdoors while engaged in agricultural labor and construction.
In the US, the Biden administration has spent the past three years formulating the first federal rules to protect workers from extreme heat, although these regulations are likely to be wound back by the incoming president, Donald Trump.
Higher youth mortality from heat in a country like Mexico is influenced by the fact there are more younger people than old in the population as well as risks such as working under the beating sun in fields, said Kristie Ebi, an epidemiologist at the University of Washington, who wasn’t involved in the research.
“However, routine exposure to higher temperatures also increases acclimatization, which should lead to lower risk,” Ebi said, adding that more research was needed to fully understand this pattern and if it extended to other countries.
“This study provides greater nuance in understanding how different segments of the population might be affected by rising temperatures and it is possible that, at least in Mexico, climate change may lead to a greater number of heat-related deaths in younger people,” said Sameed Khatana, a Penn Medicine physician and researcher whose own work has found that heat-related cardiovascular deaths are set to surge in coming decades due to the climate crisis.
Khatana said that younger people are exposed to heat through work, school and recreational activities and “therefore may experience a disproportionate impact from climate change”.
“This highlights the importance of thinking of targeted measures, such as work breaks for people working in hot environments, or rescheduling sporting events to avoid extreme heat,” he said.
