The killer heat hits young people harder than older people

A surprising study of temperature-related deaths in Mexico is upending conventional thinking about which age group is hit hardest by heat. Researchers found that at higher temperatures and humidity, the heat kills many more people under 35 than those over 50.

For decades, health and weather experts have warned that the elderly and the youngest children are the most vulnerable in heat waves. But this study of all deaths in Mexico from 1998 to 2019 shows that when the combination of humidity and temperature reaches uncomfortable levels, such as mid to upper 80 degrees Fahrenheit (about 30 degrees Celsius) and 50% relative humidity, there is almost 32 deaths were. temperature-related deaths of people aged 35 for every temperature-related death of someone aged 50 and over.

The study in Friday’s magazine Scientific progress shows a particularly surprising spike in heat-related deaths in an age group considered young and robust: people aged 18 to 35. In that age group alone, there were nine times as many temperature-related deaths as in people over 50 years old.

Study authors and outside experts are trying to figure out why. Demographics alone do not explain why more young adult Mexicans die in the heat than their elders. Two theories: outdoor workers who cannot escape the heat, and young people who do not know their limits.

According to computer simulations by the research team, the trend is likely to expand as the world warms due to human-induced climate change.

“We found that younger people are especially vulnerable to humid heat,” said co-author Jeffrey Shrader, a climate economist at Columbia University. “As the climate warms, we’re really going to shift the burden of temperature-related mortality toward younger individuals and away from older individuals who tend to be more vulnerable to cold temperatures.”

Cold weather data shows that there are more than 300 deaths among Mexican residents aged 50 and older for every young person who dies from cold temperatures, according to the study.

“People of all ages are increasingly at risk from rising temperatures, and this study shows that those we might consider relatively safe from heat-related adverse health outcomes may not be so bad,” said Marina Romanello, executive director of The Lancet Countdown that monitors the health effects of climate change. She was not part of the research team.

“Heat is a far more dangerous silent killer than most people recognize, and that heat is increasingly endangering our health and survival,” Romanello said in an email.

The study authors decided to examine weather-related deaths in Mexico because that country not only has detailed mortality data, but also has a variety of different climates, making it an ideal place to study in depth, Shrader said.

Researchers also want to find out if this is just a situation in Mexico or if other warmer parts of the world experience similar spikes in deaths among young adults during high heat and humidity.

Initially, the team only wanted to look at deaths and what scientists call wet bulb temperatures, but when they looked at age differences, they were surprised and looked in more detail, Shrader said. Wet bulb temperature, which is meant to reflect how the body cools itself, is derived using a complex measuring system that takes humidity and solar radiation into account. It is assumed that there is a wet bulb temperature of 35 degrees Celsius (95 degrees Fahrenheit). the limit to human survival. Most places don’t reach that level.

Researchers determined temperature-related mortality through a complex statistical analysis that compares numerous factors in the number of deaths and removes everything they can except temperature fluctuations, said co-author Andrew Wilson, a climate economics researcher from Columbia.

Researchers also calculated the ideal temperature when there will be the fewest excess deaths in each age group. Younger adults’ sweet temperature spot is about nine degrees Fahrenheit (five degrees Celsius) cooler than for older people, Shrader and Wilson said.

Some outside health and climate experts were initially surprised by the higher youth mortality observed in the study. Co-author Patrick Kinney, a professor of urban health and sustainability at Boston University, said it was likely that the study included a higher proportion of outdoor workers exposed to heat than previous studies.

Study co-author Tereza Cavazos, a climate scientist at the Ensenada Center for Scientific Research and Higher Education in Mexico, said she remembers her father’s generations taking siestas on the high heat of the day and that was healthy. That doesn’t happen very often now, she said.

“There’s a lot of population that is vulnerable in the future. Not even in the future, right now,” Cavazos said. She said it three Mexican heat waves This year it hit the center of the country and kept the deadly heat going overnight, leaving people with little relief. Typically, cool nights allow a body to recover.

Younger people often have a sense of invulnerability to extreme weather events and do things that increase their risk, such as exercising in the heat, Cavazos said.

“High humidity makes it much harder for the body to cool itself through sweating – which is how our bodies primarily stay cool,” says Dr. Renee Salas, an emergency room physician and climate change expert at Massachusetts General Hospital and Harvard Medical School. She was not part of the research team. “So someone who is young and healthy and working outside in heat and high humidity can reach a point where the body can no longer cool itself safely, causing a fatal form of heat injury called heat stroke.”

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