As climate change pushes global temperatures higher, attention has focused predominantly on the threat that heat poses to older adults, whose physiology makes them more susceptible to health complications.

But a study published on Friday in the journal Science Advances found that certain types of young people — including seemingly hardy working-age adults — may also be particularly vulnerable to rising temperatures.

The researchers analyzed deaths in Mexico from 1998 to 2019 and discovered that people younger than 35 accounted for three-fourths of heat-related fatalities.

“These age groups are also quite vulnerable to heat in ways that we don’t expect even at temperatures that we don’t think of as particularly warm,” said Andrew Wilson, a first author of the paper and an environmental social scientist at Stanford University.

Measuring heat-related deaths is complicated, since death certificates rarely name heat as a cause. A proximate cause of death, like cardiovascular failure, is often listed instead.

To get around this, Dr. Wilson and his colleagues used a common statistical approach to estimate how daily mortality rates across Mexico change in response to fluctuations in the “wet bulb” temperature, a measurement that uses humidity and air temperature to capture how well humans can cool their bodies through sweating.