Adults aged 60 and over may face harmful and potentially fatal heat stress at just 1.5C of global warming above preindustrial levels, according to a study in The Lancet Public Health. Younger adults may not reach the same risk threshold until warming reaches 4C.
The study says uncompensable heat stress occurs when the body can no longer cool itself, increasing the risk of serious illness and death. Older adults are especially vulnerable because they sweat less, their hearts work harder in heat and their blood vessels are less able to widen.
What the study found
Researchers led by health academics from Stanford University in California examined heat risks across younger adults aged 15 to 39, middle-aged adults aged 40 to 59 and older adults aged 60 and over. The study says earlier research applied heat-balance thresholds developed for younger people to all age groups, underestimating older adults’ risk, including the risk of heart attacks.
Uncompensable heat stress is projected to become more common across every age group as global temperatures rise. Each additional degree of global heating exposes roughly one million more people to at least 180 hours of this heat stress each year, with older adults bearing a disproportionate share of the burden.
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Why the risk is growing
The combination of rising temperatures and a projected doubling of the global population aged 60 and over to 2.1 billion by 2050 means more older people are expected to face heat-related health problems. The study identifies low- and middle-income countries, including India and Pakistan, as especially affected.
The authors warn that continued warming could make parts of the tropics and subtropics uninhabitable, particularly for older people. The study also says heatwaves will affect far more people and last longer than previously estimated when age-specific vulnerability is taken into account.
What the findings mean for health services
The UK Health Security Agency has warned that high temperatures in Britain in 2026 could produce the country’s highest annual number of heat-related deaths. A four-day heatwave in May and an eight-day heatwave in June were associated with 2,877 excess deaths, compared with 1,504 during summer 2025.
Health professionals say heat can worsen dehydration, collapse, heart disease and kidney disease among older patients. The Royal College of Physicians described extreme weather as a patient safety issue, while one hospital doctor reported a geriatric ward reaching 36C during the summer’s extreme heat.
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