Extreme heat has a harsher effect on older people than doctors previously thought. Researchers in the USA have said that the body's tolerance for heat goes down in older people. The continuing rise in global temperatures could increase the risk of illness or death for those aged 60 and over. The threat of rising temperatures to the over-60s has been seriously underestimated. The researchers said heatwaves will put millions of older people at risk of heat stress. This is when the body loses its ability to cool itself. It can damage the body and can even lead to death.

The researchers warned that "intolerable heat" will be experienced for longer periods of time. This will affect many more people than doctors thought. The over-60s are at risk because of three physical factors — they sweat less, their hearts have to work harder, and their blood vessels expand more slowly. These things limit the body's cooling functions. A director at the charity Age UK found the study alarming. She said: "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 at the highest risk.