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A deadly heat wave . 

As temperatures climbed past 110 degrees Fahrenheit (43.3 Celsius) in India on May 7, campaigning politicians, local news announcers and voters waiting in long lines .

From as far north as Japan to as far south as the Philippines, the relentless heat wreaked havoc on everyday life. Students and teachers in Cambodia were as their hand-held fans provided little protection against the stifling heat and humidity in their poorly ventilated classrooms. saw their crops wither and mourned the loss of livestock that perished under the punishing sun. from the heat.

Most of the planet has suffered the dire effects of extreme heat in recent years.

A weekslong heat wave in the southwestern United States in 2023 was described as "" in Phoenix, where temperatures hit . At the same time, Europe saw unprecedented high temperatures that in Greece.

Regardless of where or when a heat wave strikes, one pattern is a constant: from extreme heat, and this crisis will worsen in the coming years.

We study and . documents two global trends that together portend a dire future.

More older adults will be at risk of heat stress

First, temperatures are hotter than ever. from 2015 and 2023 had the highest average temperatures since global records began in 1880.

Second, the population is aging worldwide. By 2050, the number of people ages 60 and older will double to , making up 21% of the global population. That proportion is 13% today.

These combined forces mean that ever-rising numbers of vulnerable older adults will be exposed to intensifying heat.

To understand the risks ahead, we developed population projections for different age groups and combined them with for the coming decades. Our analyses show that by 2050, more than 23% of the world population ages 69 and older will be living in regions where peak temperatures routinely surpass 99.5°F (37.5°C), compared with just 14% today.

That means that as many as 250 million additional older adults will be exposed to dangerously high temperatures.

Mapping the data shows that most of these older adults live in lower- and middle-income countries with insufficient services and limited access to electricity, cooling appliances and safe water.

In historically cooler regions in the Global North, including North America and Europe, rising temperatures will be the main force driving older adults' heat exposure. In historically hotter regions in the Global South such as Asia, Africa and South America, population growth and increases in longevity mean that steeply rising numbers of older adults will be exposed to intensifying heat-related risks.

Policymakers, communities, families and older residents themselves need to understand these risks and be prepared because of older adults' special vulnerabilities to heat.

Extreme heat is especially harmful to older adults

High temperatures are oppressive for everyone, but for .

Extreme heat worsens common age-related health conditions such as heart, lung and kidney disease and can . Older people as younger people, which makes it harder for their bodies to cool down when temperatures spike. These problems are intensified by common , such as anticholinergics, which further reduce the capacity to sweat.

Spending time outdoors in hot humid weather can cause dehydration, a problem worsened by the side effects of such as diuretics and beta-blockers. Dehydration can make older adults weak and dizzy, increasing their risk of falls and injury. These threats are even worse in regions lacking access to .

Poor makes it difficult to breath, especially for those who already have lung problems such as chronic obstructive pulmonary disease, or COPD.

For older adults with physical health problems, temperatures as (26.7 C) can pose significant danger. And when humidity is as high as 90%, even 78 F (25.6 C) can be hazardous to older adults.

is especially harmful for older adults whose homes lack air conditioning or who to run their air conditioners for long periods. The ideal temperature for older adults' restful sleep is , and sleep quality diminishes as temperatures rise. can make an older adult more depressed and confused during their waking hours. Medications also can if stored in places much warmer than 77 F (25 C).

Older adults also may suffer emotionally during stifling heat waves

Being stuck indoors when temperatures are unbearable can make older adults bored, . People with may underestimate the dangers of extreme heat or may not understand the heat advisories.

Those who have can't easily travel to public cooling centers - if there is one nearby - or find relief in ," such as parks and lakes.

These threats are especially dire in , where older adults are more likely to live in substandard housing and lack access to high-quality health care or ways to cool down in the heat. We talk about this as "."

What can be done?

Policymakers can work to cut greenhouse gas emissions from fossil fuels in vehicles, power plants and factories, which drive global warming, and develop effective plans to protect older people from heat risk. Older adults and their caregivers also can take .

But efforts to help need to be tailored to each region and population.

Wealthy municipalities can in early and ride services to cooling centers and hospitals. They can use geographic information systems to identify neighborhoods with high concentrations of older adults and expand power grids to manage increasing demand for air conditioning.

In regions with substandard housing, limited access to clean water and few public supports such as cooling centers, are necessary. Providing better health care, water and housing and reducing air pollution that can require significant changes and investments many countries struggle to afford.

The World Health Organization and Pan American Health Organization warn that for preparing communities to handle rising heat and the risk to aging populations. Across all regions, researchers, practitioners and policymakers could save lives by heeding their call.