Rising heat is disproportionately killing young adults
As the Earth gets warmer, the assumption that elderly individuals have the highest risk of succumbing to heat is being challenged.
The findings from a recent study in Mexico show a contrasting reality: three-quarters of heat-related mortalities are happening among individuals who are under the age of 35, with a significant proportion being between 18 and 35.
This is an unexpected outcome, considering this age group is thought to be most resilient to heat.
Mortality rates and wet-bulb temperatures
Jeffrey Shrader is a key expert behind the study, which was conducted by researchers from the Center for Environmental Economics and Policy affiliated with Columbia University’s Climate School.
“It’s a surprise. These are physiologically the most robust people in the population. I would love to know why this is so,” said Shrader.
Mexico, with its comprehensive geographical data on both daily temperatures and mortality, proved to be an ideal place for this exploratory study.
The researchers scrutinized the correlation between excessive mortality rates and wet-bulb temperatures – a scale measuring the amplified effects of heat when combined with humidity.
Young adults and heat-related deaths
According to the analysis, Mexico averaged around 3,300 heat-related deaths each year from 1998 to 2019.
A shocking third of these deaths were observed among 18 to 35-year-olds, a figure that is wildly disproportionate to the representation of this age group in the population size.
Infants and children under 5 were found to be highly vulnerable as well. On the other hand, people aged 50 to 70 suffered the least heat-related mortality.
“We project, as the climate warms, heat-related deaths are going to go up, and the young will suffer the most,” explained R. Daniel Bressler, the study’s co-lead author and a Ph.D. candidate in Columbia’s Sustainable Development Program.
Factors that influence heat vulnerability
Several factors could be contributing to this unexpected trend. Young adults are more likely to be engaged in outdoor labor, such as farming and construction, which may expose them to dehydration and heat stroke.
This vulnerability is also applicable to indoor manufacturing in spaces that lack air conditioning.
The researchers highlighted that younger, less experienced workers face greater heat risks due to their low position and strenuous work. Participation in rigorous outdoor sports was another risk factor linked to young adults.
The susceptibility of infants and small children may be attributed to the fact that their smaller bodies absorb heat more quickly and their underdeveloped sweat glands limit their ability to cool off.
The still-developing immune systems of these children also put them at risk to illnesses that are more prevalent in humid heat.
Surprising heat mortality trends
Wet bulb temperatures, often converted into Fahrenheit “real-feel” heat indexes by the media, play a crucial role in understanding this mortality pattern.
Young people experience the least mortality at wet-bulb temperatures around 13o C (71o F with 40% humidity).
However, the researchers found that the highest number of deaths occurred at somewhat lower wet-bulb temperatures, primarily due to the higher frequency of these temperatures – which expose more people to harmful conditions.
The experts also found a surprising trend in the among older adults, who mainly died not from heat but from modest cold.
Elderly individuals have lower core temperatures that make them sensitive to cold and they consequently stay indoors, increasing their exposure to infectious diseases.
Although global warming receives extensive attention, cold weather is currently the leading cause of temperature-related death globally, including in Mexico.
However, the proportion of heat-related deaths has been steadily increasing since 2000, and this trend is likely to persist.
Global implications of rising temperatures
The implications of the research extend far beyond Mexico, shedding light on a global issue with potentially devastating consequences.
Countries in Africa and Asia that are predominantly hotter, poorer, and with youth that engage in manual labor could see massive heat-related mortality rates in the future.
The researchers plan to validate their findings by extending the research to other countries, including the United States and Brazil. The goal is to gain a deeper understanding of this alarming trend.
The full study was published in the journal Science Advances.
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