A person who is 40 today will be about 70 years old in 2050. The world is undergoing unprecedented and inexorable change: scientists predict that by 2050, more than 20% of the world’s population will be over 60. This demographic shift coincides with another major change: the warming of the Earth due to human-caused climate change.
The combination of the two poses a huge risk, says Giacomo Falchetta, lead author of a new paper published Tuesday in Nature Communications. Taken together, the number of people at risk from chronic extreme heat worldwide will at least double by 2050, he says. The number of older people regularly exposed to both chronic and acute heat will increase by about 200 million worldwide by mid-century, and slow action on climate change today could increase that number significantly, he says. Because demographic changes are locked in, “it’s not a question of if, but a question of when.”
In Europe, North America, and parts of East Asia, the population has rapidly become skewed toward older people. Even in regions where the number of young people is growing, like much of Africa, where the median age on the continent is now 19, the number of older people is also increasing. By 2050, those 19-year-olds will be approaching middle age.
Demographic shifts alone would put millions of people at greater risk even if human-caused climate change were not part of the equation. But it is.
“The reality here is that we’re not living in a world where the climate is the only thing changing,” says Kai Chen, an environmental epidemiologist at Yale University who was not involved in the study. But climate change “amplifies so many things that we’re already trying to deal with,” he says. His team recently published a similar study that found that further climate change will lead to more older people dying each year from exposure to climate-induced heat. These are preventable deaths, Chen emphasizes.
The new study combined heat risk maps with maps of where people over 69 live now and in 2050. Health risks increase for older adults above that threshold. The researchers also looked at extreme heat — when and where temperatures rise above 99.5 degrees Fahrenheit or pass unusually high limits for a given area.
The results were staggering. Even in a world with aggressive climate mitigation measures, 160 million people will be living with 30 or more sweltering days a year by 2050. With less effective climate action, that number could be 250 million.
Europe is ageing faster than anywhere else in the world. It is also warming faster than the global average. This means that by 2050, the number of older people exposed to chronic heat could increase fivefold. Since anywhere from 20 to 25% of the total population could be over 69, millions of people will be living through hotter years. Severe heatwaves, like the one in 2022 that 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 for rising risk. But in Africa, Asia and South America, changing demographics are a bigger factor. Big changes are looming for countries like China and India, where large cohorts of people in their 40s and 50s are living longer than ever before.
As we age, our bodies become less able to cope with heat. This is due to both physical changes and social or cultural ones.
From a physical standpoint, explains Julia Jernberg, a physician and researcher at the University of Arizona in Tucson, older people sweat less efficiently. And their instinct to drink water is also weakened, which can lead to dehydration and then less sweating. On top of that, “often our older patients, or those of us who are older, don’t have the necessary cardiac pumping mechanism” to efficiently move blood from the core to the blood vessels near the skin, where it can be cooled by sweating, she says.
In acute heat stress, blood clotting and inflammation spiral out of control, Jernberg says. In the worst case, heat can trigger cell breakdown. The debris enters the bloodstream and can trigger an immune response. “It’s like your body is breaking down from the heat. You’ve reached a tipping point. And in older patients, it’s much more lethal,” Jernberg says.
Social and cultural norms also play a role. For example, older members of the Falcetta family in southern Italy resisted buying an air conditioner for years because they never needed one. But the intense heat of 2021, along with persistent urging from Falcetta and other family members, pushed them to buy one. But they still don’t like using it, Falcetta says.
In the U.S., the aging population is increasingly made up of people of color and those with limited financial resources, says Safia Okoye, a nurse practitioner and researcher at Drexel University in Pennsylvania. Financial barriers to staying cool and safe abound. “Is your home designed to handle the heat? Do you have good ventilation, good windows that you can open and close, air conditioning or fans — and if you have them, can you pay the bills?” she asks — and the answer to many of those questions for older Americans is already “no.”
There are also practical issues. Okoye has worked with patients who have mobility issues and are trying to limit their water intake so they don’t have to use the toilet as often. This can lead to dehydration, which can increase the risk of heat.
In the U.S., the results of these risk studies point to clear priorities for addressing the problem, Okoye said. One approach, she said, is to invest in home repairs, insulation, and other ways to keep seniors’ homes at a comfortable temperature. Programs that help pay for energy costs or improve efficiency can also help seniors, especially those on low incomes, feel comfortable using air conditioners or cooling technologies.
It’s also important to address the “social connection aspect” of heat resilience, Okoye says. Social connections saved lives during the 1995 Chicago heat wave. Now, programs that help seniors check in on each other regularly can help them stay safe during disasters. Or it could be friends and family who can help them get to cooling centers during dangerous heat waves.
At the national and international level, says Yale’s Kai Chen, the first step is recognizing the scale and urgency of the problem. Demographic changes are already happening and are essentially unstoppable, he says. But how much heat older people are forced to endure is still modifiable. That means that any climate action that takes place now “will have much greater benefits in the future than they do today,” says Chen. And those benefits will be felt directly by those in their 30s and 40s today.
Russian demographers have analyzed the impact of heat waves on excess mortality in large cities and small towns and have discovered evidence that this figure rises by 46% in megacities, while in rural areas it increases by approximately 17%. This was reported by TASS, citing the press service of the National Research University Higher School of Economics.
Scientists came to this conclusion while studying the consequences of a powerful heat wave that hit many regions of Russia in July and August 2010, including the Moscow Region, the Black Earth Region, and the Volga-Vyatka Region. This weather anomaly not only led to the establishment of consistently high air temperatures, but also provoked a series of forest and peat fires, the smoke of which negatively affected the health of Russians.
Russian demographers were interested in whether there were differences in how this weather cataclysm was endured by residents of large and small settlements. The fact is that in the territory of large megalopolises, due to dense development, a large number of roads and industrial facilities, a “heat island” is formed, in which the ambient temperature can be up to 7° higher than in rural areas.
To create a model of excess mortality, the researchers combined satellite data on temperature, Rosstat information on mortality, and retrospective data on temperature and air pollution. Based on this data for 2005–2009, taking into account the age composition of the population, they modeled the expected excess mortality of 2010 and compared it with the actual one.
The researchers’ calculations showed that the heat had a much stronger effect on excess mortality in cities with populations of over half a million people (46% increase) than in rural areas (17% increase). Moscow experienced the greatest impact of the heat, where the peak increase in some weeks was more than 150%. Such differences in the impact of heat waves on mortality in large and small towns should be taken into account when developing measures to counteract these weather anomalies, the scientists concluded.