Everyone you know will eventually be highly vulnerable to extreme heat

Zahra Hirji

When a heat dome shattered temperature records across the Western US and Canada in June 2021, the resulting fatalities exposed a pattern. In Portland, Oregon, and surrounding Multnomah County, 56 of the 72 people who died were aged 60 and up. In British Columbia, people 60-plus accounted for 555 of the 619 fatalities. Just over a year later, a sizzling June, July and August in England caused roughly 2,800 excess deaths among people 65 and older. More than 1,000 of them occurred over four days in late July.

Elderly residents sit in the shade a heat wave in Ourense, Spain on Aug. 8, 2023.

Intense heat waves in recent years offer a stark warning of what’s at stake for humanity. The planet just endured its 12 hottest consecutive months on record, and this summer threatens to be hotter than ever. But those stakes are not experienced equally across age groups. Older adults are more at risk of experiencing dangerous health impacts during periods of intense heat.

“Older adults are one of the populations that we classically see as being more vulnerable to the effects of climate change, specifically to effects of extreme heat,” says Catharina Giudice, an emergency physician and climate change and human health fellow at Harvard’s FXB Center. “As we age, our ability to adapt to heat diminishes.”

When confronted with rising temperatures, the human body has two main tools for thermoregulating, or avoiding overheating. The first is sweat, which releases heat when it evaporates. Compared to young and middle-aged people, “older people don’t sweat as much,” says Deborah Carr, a professor of sociology at Boston University who studies aging. “They have essentially a less efficient cooling system. So they’re in extreme heat and don’t sweat it out.”The second tool is increased circulation of blood, which draws heat from deep inside the body to the skin, where it can escape. “The heart has to sometimes pump two to four times more blood each minute than it would on a cooler day,” says Renee Salas, who is affiliated with the Center for Climate, Health, and the Global Environment at Harvard’s T.H. Chan School of Public Health.

A healthy heart can handle all that extra pumping, but people suffering from heart disease and other cardiovascular issues may struggle. Older people are more likely to have those conditions, as well as other chronic issues like diabetes, hypertension, and lung problems, all of which can inhibit the body’s ability to respond to heat. Many of the medications used to treat those and other health conditions also impair that response, such as by decreasing the ability to sweat or increasing urination that can trigger dehydration.

“Medications kind of ironically can amplify some of those heat effects,” Giudice says.

The warning signs of dangerous heat can also be more difficult for older people to self-identify. That’s because in general, older adults “don’t sense heat the same way,” says Glen Kenny, a University of Ottawa physiology professor who studies heat impacts on the body.

If a young or middle-aged person were sitting in the heat, Kenny says, they might find it hard to tolerate, while an older person in the same heat “might say, ‘I’m OK.’” The cause of this gap in reported heat symptoms remains unclear, but research done by Kenny and his team shows that it can be hazardous: By the time an elderly person feels acute discomfort due to high temperatures, their body may already be suffering significantly.

And those are just the physiological disadvantages. Many older adults also live alone and are socially isolated, making them less likely to have a support network. In British Columbia in 2021, for example, Kenny says many of the older people who lost their lives were “living alone” and “had no support or family members” to check in on them as the heat wave dragged on.

All of these risks exist today: Global average temperatures are already 1.2C above pre-industrial levels, and heat waves are more frequent and more intense than they were just a few decades ago. This year alone, excessive heat has prompted school closures, pushed power grids to their limit and claimed lives around the world. But as the planet continues to warm, the elderly’s share of its population is also increasing. In 2021, there were roughly 1.1 billion people 60 years or older globally; by 2050, that’s projected to hit nearly 2.1 billion people. In the coming decades, far more older adults will be exposed to dangerous levels of heat than are today.

“There is a general trend in improvement in life expectancy,” says Giacomo Falchetta, a climate researcher at the Italian research institution CMCC and lead author on a study of heat exposure for older adults that was published in Nature Communications in May. “People are living longer because of better access to health care, better access to nutrition,” Falchetta says. But “climate change is increasing the frequency and intensity of heat exposure.”

The study, which Carr at Boston University co-authored, projects that by 2050 roughly 24% of the global population at least 69 years old will be living in places where maximum temperatures exceed 37.5C (99.5F). At that point, between 177 million and 246 million more older adults will be exposed to dangerous heat than are now.

Falchetta frames those conclusions as actionable: He hopes the research will inform city and country officials about heat’s growing threat so they can plan to better protect their older citizens.

Some already are. Cities from Miami to Melbourne are expanding access to air-conditioned public places known as cooling centers, while also adding more shading and planting more trees.

In Athens, officials have formally identified people over 60 years of age as among the most impacted by rising heat. Social workers there check on the elderly and offer them transportation to cooling centers, according to Elissavet Bargianni, Athens’ chief heat officer and head of the city’s Resilience and Sustainability Department.

In Canada, University of Ottawa researchers and government officials collaborated on a health check guide, released in 2022, that’s meant to help people identify those for whom heat is particularly risky. The guide, which includes directions on how to assess someone’s health status and keep them cool, also details what to ask a loved one from afar, such as the temperature of their home and how they’ve been sleeping.

“Many susceptible people may not recognize when they are overheating, but another person can help identify a risky situation with some careful questions and observations,” Sarah Henderson, scientific director of Environmental Health Services at the BC Centre for Disease Control and the National Collaborating Centre for Environmental Health, said in a statement when the guide was released. “Check in as often as possible. At least twice a day and once in the evening when it is hottest indoors.”