A person in their 40s now will be nearing 70 in the year 2050. And they won't be alone, because the world is undergoing an unprecedented and inexorable shift: by 2050, scientists project, more than 20% of Earth's population will be over 60.
That demographic shift coincides with another major change: the Earth heating up because of human-caused climate change.
The confluence of those two factors represents an enormous risk, says Giacomo Falchetta, the lead author of a new paper published Tuesday in Nature Communications. Combined, the number of people at risk worldwide from chronic extreme heat is set to at least double by 2050, he says. The number of older people regularly exposed to both chronic and acute heat will grow by about 200 million people worldwide by mid-century—and slow climate action today could push that number up much higher, he says.
"The heat that elderly individuals are exposed to throughout the year could grow up to five-fold, on a global scale," Falchetta says—an enormous increase in number and risk.
Because the demographic changes are locked in, "this is not a question of if, but when," says Falchetta. But, the research shows, the intensity of the risk exposure for the aging population can still be lowered, if planet-heating greenhouse gas emissions are reined in aggressively and countries develop effective plans to protect older people from the heat risk.
An aging population worldwide
In Europe, North America, and some countries in East Asia, the population has quickly become weighted toward older people. Even in regions where the number of young people is growing—like in most of Africa wherethe median age across the continent today is 19 years old—the number of older people is also getting bigger. By 2050, those 19-year-olds will be nearing middle age.
The demographic shifts alone will put millions of people more at risk, even if human-driven climate change wasn't a part of the equation. But it is.
"The reality here is, we don't live in a world where only climate is changing," says Kai Chen, an environmental epidemiologist at Yale University who was not involved in the research. But climate change "is amplifying so many things we're already struggling to handle," he says. His team recently published a similar study, which found thatfurther climate change will push up the number of older people who die of climate-change-driven heat exposure each year. Those are avoidable deaths, Chen stresses.
The new study merged maps of heat risk with maps of where people over the age of 69 live now and in 2050. They looked at exposure to chronic heat by counting the number and intensity of days each year when someone might need to cool their environment to 75 degrees Fahrenheit. Health risks grow for older people above that threshold. Researchers also looked at acute heat—when and where temperatures go above 99.5 Fahrenheit, or pass unusually hot limits for a particular area.
The results were stark. Even in a world with strong climate mitigation, 160 million people will live through 30 or more sweltering days each year by 2050. With less effective climate action, that number could be 250 million.
Europe is aging more quickly than almost anywhere else in the world. It's also heating up faster than the planetary average. That means by 2050 the number of older people exposed to chronic heat could increase by a factor of 5. Since somewhere between 20 to 25% of the total population could be over 69, millions more people will live through hotter years. Acute heat waves, like the one in 2022 that study estimates say killed more than 60,000 people across the continent, will also become more frequent, putting more people at risk.
In Europe and North America, climate change is the factor that matters most to the growing risk. But in Africa, Asia, and South America, shifting demographics are the bigger driver. Major changes are slated for countries like China and India, which have large cohorts of people in their 40s and 50s living longer than ever before.
Today, about 30 million people in the U.S. live with chronic heat exposure, mostly in the south and southeast. By 2050, that number is projected to grow to about 20% of the country's population. And every year, an increasing percentage of those older Americans are low-income and elders of color, who are more likely to have medical conditions making them sensitive to heat, or social scenarios limiting their ability to handle it.
"Population aging is not a problem," says Deborah Carr, one of the paper's authors and an expert on aging at Boston University. "We want our population to age! We want to benefit from the wisdom of older adults. We want to celebrate them living longer."
Instead, she says, "Climate change is the problem we need to face. What we need to do is to change the planet to accommodate these needs of people who increasingly have the good fortune to live to older ages."
Why are older people more sensitive to heat?
As people age, their bodies become less adept at handling heat. That's because of both physical changes and social or cultural ones.
Physically, explains Julia Jernberg, a doctor and researcher at the University of Arizona in Tucson, older people sweat less effectively. And their instincts to drink water also drop, which can lead to dehydration—and then less sweating. On top of that, "a lot of times our older patients, or those of us who are older, don't have the cardiac pumping mechanism necessary" to move blood as efficiently from their core to blood vessels near the skin, where it could be cooled by sweating, she says.
At acute levels of heat stress, blood clotting and inflammation go haywire, Jernberg says. In the worst cases, heat can drive cellular breakdown. The broken bits get dumped into the bloodstream and can trigger an immune response. "It's like one's own body is disintegrating from the heat. You've reached the tipping point. And in older patients [that process] is much more lethal," Jernberg says.
Social and cultural norms are also at play. Falchetta's older family members in southern Italy, for example, resisted getting an air conditioner for years because they never needed one. But a massive heat wave in 2021, plus urgent prompting from Falchetta and other family members, pushed them to buy one. They still don't like to use it, though, says Falchetta.
In the U.S., the aging population is increasingly made up of people of color and people with limited financial resources, says Safiyyah Okoye, a nurse practitioner and researcher at Drexel University in Pennsylvania. Financial barriers to keeping cool and safe abound. "Is your house suitable to handle the heat? Do you have good ventilation, good windows that can open and close, AC or fans—and if you do have them can you pay the bills?" she asks—and the answer to many of these questions for older Americans already is "no."
There are practical challenges, as well. Okoye has worked with patients who have mobility concerns and try to limit how much water they drink so they won't have to frequently use the bathroom. That can lead to dehydration, which can increase their heat risk.
That's a different problem to solve than if someone is sweating less because of a medication, Okoye says. "It's really important when we see a population at risk for us to ask why—to see who exactly is at risk—because that is how we're going to come up with specific solutions," she says.
Is there a solution?
Within the U.S., says Okoye, the results of these risk studies point to clear priorities to address the problem. One approach, she says, is investing in home repair, insulation, and other ways to keep seniors' homes at comfortable temperatures. Programs that help pay for electricity costs or efficiency upgrades can also help older people, especially lower-income seniors, feel comfortable using air conditioners or cooling technologies.
It's also critical, Okoye says, to address "the social connection aspect" of heat resilience. Social connections saved lives during the 1995 Chicago heat wave. Now, programs that help older people check in on each other regularly could help keep them safe during disasters. Or it could be friends and family that assist them to cooling centers in times of dangerous heat.
"What it boils down to me is this message, that now is the time we must act," says Sue Anne Bell, a nurse-scientist who studies disasters and health care at the University of Michigan. "Here's the data, now we know it. We have to do something about it."
At the national and international level, says Yale's Kai Chen, the first step is to recognize the scale and urgency of the problem. The demographic changes are already in motion, and essentially unstoppable, he says. But how much heat older people are forced to experience is still malleable. That means for any climate action that happens now, the "benefits will be much larger in the future than today," Chen says. And those benefits will be directly felt by those in their 30s and 40s today.
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