The scientists warn that as global temperatures continue to rise, people aged 60 and over face a growing risk of serious illness or even death during heatwaves. They explain that extreme heat can lead to a condition called uncompensable heat stress, where the body can no longer cool itself, which may cause severe damage or be fatal.

The higher vulnerability of the over‑60s is linked to three physical changes. First, they sweat less, so evaporative cooling is reduced. Second, their hearts must pump harder to move blood to the skin, increasing cardiac strain. Third, their blood vessels expand more slowly, limiting the flow of heat away from the core.

These factors are especially worrying for older people living in low‑income countries, where access to cooling and medical care is often limited. A director at the charity Age UK described the findings as alarming, noting that extreme heat now represents a very real health threat to the older population.

Because heatwaves are expected to become more frequent and last longer, protecting seniors—by providing shade, hydration, and monitoring—will be essential to prevent uncompensable heat stress and its deadly consequences.