Hidden Danger: Why Extreme Heat Poses a Severe Threat to the Elderly Amid Climate Change

A new study conducted by researchers at Stanford University in the United States reveals that a significantly higher number of elderly individuals than previously estimated face severe health risks or death from extreme heat as climate change accelerates global temperatures.

By accounting for how aging diminishes the body's natural heat tolerance, the Stanford study highlights unprecedented climate risks for the global population. With the demographic of individuals aged 60 and older projected to more than double from one billion in 2020 to 2.1 billion by 2050—accounting for 21 percent of the global population—the research warns that rising temperatures could prove far more fatal than anticipated.

“Previous assessments often assumed that everyone could tolerate heat as well as a healthy young adult, which substantially underestimated the risk to older people,” Chris Mullington, honorary clinical senior lecturer at Imperial College London in the United Kingdom, told Al Jazeera. The new study “reinforces that dangerous heat cannot be defined by one universal temperature threshold. It depends partly on who is being exposed.”

As people age, the body's natural cooling mechanisms degrade: individuals sweat less, and blood vessels fail to expand adequately, forcing the heart to work harder. Eventually, the body reaches a critical threshold known as “uncompensable heat stress,” a point that older adults hit much sooner and at lower temperatures than younger counterparts.

Researchers discovered that individuals aged 65 and older experience uncompensable heat exposure at 1.5C of global warming above preindustrial levels at a rate comparable to what younger adults would face at 4C of warming. Current long-term global warming is estimated at approximately 1.4C above preindustrial levels. While the European Union’s Copernicus agency noted that the annual global average surpassed 1.5C for the first time in 2024, multidecade long-term warming has not officially crossed this threshold.

Nevertheless, Stanford researchers estimate that the population experiencing at least 180 hours annually beyond their specific age group's safe heat threshold is already more than double previous estimates. Mullington clarified that these 180 hours accumulate throughout the year rather than continuously, denoting potential exposure to uncompensable conditions rather than inevitable illness for everyone exposed.

However, this indicates that older adults face dangers of heat-related illness and mortality at much lower temperatures than previously believed. “Conditions that a healthy young adult might still tolerate could already cause an older person to store heat, experience a rising core temperature and suffer serious illness including heatstroke,” Mullington stated.

Severe ambient heat can trigger medical emergencies like heatstroke, heart attacks, or death. Predicting these outcomes through global averages alone remains difficult because air temperature is an unreliable indicator of physical danger. Factors such as humidity, sunlight, air movement, clothing, physical activity, and individual cooling capacity play critical roles, according to Mullington. Furthermore, the study notes that only a fraction of heatwave deaths stem directly from hyperthermia, with most fatalities linked to exacerbated comorbidities such as cardiovascular, renal, and respiratory conditions.

Global warming is progressing at an unprecedented rate not witnessed in the past 10,000 years, according to NASA data cited in the research. Concurrently, increasing life expectancies and declining fertility rates are driving a rapidly aging global population, amplifying vulnerability to severe heat.

Low-income nations including China, India, and Pakistan face the highest risks even at 1.5C of warming, with affected geographical areas expanding as temperatures rise. The study estimates that each additional degree of global warming will subject an additional billion people to 180 hours of uncompensable heat annually, predominantly impacting older adults. At 3C of warming, the study projects that India, China, Pakistan, and Bangladesh will account for 1.5 billion people facing uncompensable heat exposure—nearly three-quarters of the worldwide total.

To mitigate these risks, Stanford researchers emphasize the importance of identifying where and when heat limits will be breached. Recommended adaptations include expanding urban green infrastructure, improving ventilation, reducing anthropogenic heat emissions, setting up cooling centres, and enhancing heat warning systems tailored to vulnerable communities like socially isolated or economically disadvantaged seniors. Because most heat-related deaths among older adults occur indoors, the study also highlights the necessity of broad access to air-conditioning supported by resilient energy infrastructure, alongside the ultimate long-term goal of reducing global emissions.