HOW HEAT AFFECTS AN AGEING BODY
The human body has two main mechanisms to cool itself: Sweating and increasing blood flow to the skin. In older adults, those processes are compromised – they sweat less and they have poor circulation compared with younger adults.
“Because older individuals are not able to release the heat as well, their core temperature goes up faster and higher,” said Craig Crandall, a professor of internal medicine specialising in thermoregulation at the University of Texas Southwestern Medical Centre. “And we know that core temperature is the primary driver for heat-related injury and death.”
These changes don’t suddenly emerge when someone reaches 65; they start gradually in middle age, said Glen Kenny, a professor of physiology at the University of Ottawa. “It’s a slow decline,” he said. But you start to see noticeable differences “by the age of 40, no question”.
Chronic conditions that are more common in old age, most notably cardiovascular disease and diabetes, can exacerbate these issues. A diseased heart isn’t able to pump as much blood, further reducing blood flow to the skin. And if the nerves become affected in people with severe diabetes, the body might not receive the message that it needs to start sweating. (Younger people with these conditions are also at a heightened risk for heat-related problems.)
As people age, they also stop feeling as thirsty and so they tend to drink less. In hot conditions, that can cause them to become dehydrated faster, which is “hugely detrimental for temperature control,” Dr Crandall said.
In addition, some older adults, particularly if they have some form of dementia or cognitive decline, may not perceive temperature changes as well. As a result, they won’t respond appropriately to heat, both biologically (through sweating) and behaviourally (by moving to someplace cool).
Finally, certain medications can affect people’s hydration, blood flow and even the sweat response, so be sure to ask your doctor about any medications you’re taking.
Of course, not everyone the same age responds to heat in the same way. Older adults who are physically fit are typically more resilient, Dr Crandall said, because they have better blood flow and they sweat more than their sedentary peers.