Young people may be at much greater risk of dying from climate change-induced extreme heat than the elderly, a new study has found
Those under the age of 35 years old made up about 75 percent of recent heat-related deaths in Mexico — with a significant share falling in the 18 to 34 range, according to the study, published on Friday in Science Advances.
The findings upended existing assumptions that older people are particularly in danger of dying from the impacts of extreme heat and that younger individuals might be more resistant to these effects, the study authors stressed.
“It’s a surprise,” co-author Jeffrey Shrader, an environmental and labor economist at Columbia University, said in a statement. “These are physiologically the most robust people in the population.”
The researchers said they chose Mexico for their study because the country collects granular data on both mortality and daily temperatures.
To draw their conclusions, they correlated excess mortality — the number of deaths above or below the average — with temperatures on what’s known as the “wet-bulb scale.” That scale is a measure of the amplified effects of heat when combined with humidity.
Ultimately, they found that from 1998 to 2019, the county experienced about 3,300 heat-related fatalities each year.
Of the total annual heat deaths, nearly a third fell in the 18 to 35 age range: a figure that the authors described as “far out of proportion with the numbers in that age bracket.”
“We project, as the climate warms, heat-related deaths are going to go up, and the young will suffer the most,” co-lead author, R. Daniel Bressler, a doctoral candidate in Columbia’s sustainable development program, said in a statement.
The researchers attributed their findings to a variety of complex factors. Although younger adults tend to be more physiologically resilient to heat, the authors pointed out several behavioral, social and economic circumstances that may be influential.
For young adult populations, heat exposures could be occurring through sports and other recreational activities, a lack of air conditioning in younger households and outdoor occupations that have limited precautionary measures, according to the study.
“These are the more junior people, low on the totem pole, who probably do the lion’s share of hard work, with inflexible work arrangements,” Shrader said.
While children under 5 — and infants in particular — were also highly vulnerable, this finding didn’t surprise the researchers. As their immune systems are still developing, they tend to be more susceptible to diseases that come with humid heat, such as mosquito-borne and diarrheal illnesses, according to the study.
What did surprise the authors, however, was the observation that people aged 50 to 70 seemed to suffer the least from such mortalities. This population tended to be at greater risk of death from modest cold, rather than from heat, the researchers found.
Although Mexico is largely tropical and subtropical, higher-elevation zones do have some chilly weather, and older people usually have lower core body temperatures — making them more sensitive to cold, per the study. They also may be more likely to stay indoors, where infectious diseases spread more easily, the authors noted.
Going forward, the researchers stressed that their findings could have global implications, pointing out that Mexico is a middle-income country with an average under-35 population share.
Hotter, poorer countries, on the other hand, may have much younger populations working in manual labor at higher percentages, the authors warned.
“Thus, if Mexico is any indicator, heat-related mortality in those nations could be massive,” they added.
