Science Adviser, 9 December 2024

Heat kills—even the young and healthy

There’s no doubt that a warming world comes with myriad health risks. Older people are especially vulnerable to the dangers of heat—but a new study surprisingly finds that young people are falling victim, too.

Researchers analyzed deaths in Mexico from 1998 to 2019. While previous studies had found that people over the age of 65 account for a third or more of heat-related fatalities, in this dataset three-quarters of heat-related deaths were in people under 35. “It’s a surprise . These are physiologically the most robust people in the population,” said study coauthor Jeffrey Shrader in a statement.

When the team drilled into the data, they found that older adults were still more vulnerable when it was especially hot, but kids under 4 and adults aged 18-35 years were dying at more moderately warm temperatures. That’s an especially alarming finding, first author Andrew Wilson tells The New York Times, because climate change will “increase the number of moderately warm days much more than … the number of extremely hot days.” According to the team’s calculations, this will lead to a 32% increase in deaths in children and young adults by 2100.

For the young kids, it’s pretty clear how even moderately hotter weather could kill: Children’s bodies aren’t as good at regulating temperature, and they’re too young to change their clothes or move to cooler locations freely. But the young adults’ vulnerability will need further examination, experts say. It may be that their working conditions or recreational activities are placing them at increased risk of overheating, for instance. Understanding exactly what’s driving their risk, the team says, will help determine the best ways to prevent those deaths.

Science Advances, 6 December 2024

Heat disproportionately kills young people: Evidence from wet-bulb temperature in Mexico

Recent studies project that temperature-related mortality will be the largest source of damage from climate change, with particular concern for the elderly whom it is believed bear the largest heat-related mortality risk. We study heat and mortality in Mexico, a country that exhibits a unique combination of universal mortality microdata and among the most extreme levels of humid heat.

Combining detailed measurements of wet-bulb temperature with age-specific mortality data, we find that younger people who are particularly vulnerable to heat: People under 35 years old account for 75% of recent heat-related deaths and 87% of heat-related lost life years, while those 50 and older account for 96% of cold-related deaths and 80% of cold-related lost life years. We develop high-resolution projections of humid heat and associated mortality and find that under the end-of-century SSP 3–7.0 emissions scenario, temperature-related deaths shift from older to younger people. Deaths among under-35-year-olds increase 32% while decreasing by 33% among other age groups.