Extreme heat may have a harsher effect on older people than doctors previously thought. Researchers from Stanford University in the USA have said that the body's tolerance for heat deteriorates in older people. They added that the continuing rise in global temperatures could pose a serious risk of illness or death for those aged 60 and over. The threat of rising temperatures to the health of the over-60s has been seriously underestimated. The researchers said heatwaves will put millions of older people at risk of a condition called uncompensable heat stress. This is when the body loses its ability to cool itself. This can cause serious damage to the body and can even lead to death.

The researchers warned: "Intolerable heat will be experienced at much larger scales and for longer durations, affecting far more people than previously thought." They said the over-60s are at a higher risk because of three physical factors — they sweat less, their hearts have to work harder in the heat, and their blood vessels expand more slowly. These three things limit the ability of the body to cool itself. A director at the charity Age UK said she found the conclusions in the study alarming. She said: "This study means there's now no denying that extreme heat poses a very real health threat to our older population." Elderly people in low-income countries are likely to be at highest risk.