Age-related chronic conditions can increase risk of heat exhaustion in older people

NEW YORK – The world is experiencing the hottest days in history. Heat waves blanketed the Northern Hemisphere last week, with temperatures reaching 37.8 deg C on three continents.

Extreme heat can be deadly for anyone, but older adults are especially vulnerable.

In the heat wave that suffocated Europe in summer 2022, people age 65 and older accounted for approximately 90 per cent of heat-related deaths.

Experts say that three factors combine to increase older adults’ risk: biological changes that occur naturally with age, higher rates of age-related chronic diseases and greater use of medications that can alter the body’s response to heat.

Here is how to gauge the risk for a heat-related illness and how to stay safe.

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 professor of internal medicine Craig Crandall, who specialises in thermoregulation, at the University of Texas Southwestern Medical Center.

“And we know that core temperature is the primary driver for heat-related injury and death.”

These changes do not suddenly emerge when someone reaches 65. They start gradually in middle age, said professor of physiology Glen Kenny at the University of Ottawa.

“It’s a slow decline, but you start to see noticeable differences by the age of 40.”

Chronic conditions that are more common in old age, most notably cardiovascular disease and diabetes, can exacerbate these issues.

A diseased heart is not 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 heightened risk for heat-related problems.

As people age, they 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”, Prof Crandall said.

Some older adults, particularly if they have some form of dementia or cognitive decline, may not perceive temperature changes. As a result, they will not respond appropriately to heat, both biologically (through sweating) and behaviourally (by moving to a cool place).

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 are 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, Prof Crandall said, because they have better blood flow and they sweat more than their sedentary peers.

How to stay safe

People often think that heat needs to be extreme (say, over 37.8 deg C) to cause illness, but in older adults, signs of heat exhaustion can emerge when temperatures are as low as 26.7 deg C.

“Twenty-year-olds can go out in 26.7 deg C weather for hours and generally be okay,” said Dr Angela Primbas, a geriatrician at UCLA Health. “That’s not true for older adults.”

Physical exertion increases a person’s risk for heat illness because the body starts to generate even more heat.

On hot days, Dr Primbas said, older adults and people with serious health conditions should limit outdoor activities such as walking and gardening to the cooler mornings and evenings, take frequent breaks and drink plenty of water.

Listen to your body too. If the activity starts to feel harder than normal, that is a signal to stop and find a place to cool down.

Signs of dehydration or heat exhaustion include dizziness, light-headedness, a headache, a racing heart or feeling lethargic.

Low energy – if someone is not talking or interacting as much as usual – is especially important to watch out for in people with cognitive impairment, who may not realise how hot they are or be able to express it.

While older adults face unique challenges when it comes to heat, the ways to cool down are the same for any age.

If anyone starts to experience any of the above symptoms, it is best to go somewhere with air-conditioning, Prof Kenny said.

The indoor temperature does not have to be “sub-zero”, he added. Just aim for 25 deg C or below.

In the absence of air-conditioning, water is “extremely helpful in reducing the risk for heat-related injury”, Prof Crandall said. He advised rubbing an ice cube over the skin, spraying yourself with cool water, drenching your shirt or taking a cool shower or bath.

Whatever you do, take heat seriously. It is the No. 1 cause of weather-related deaths in the United States and many are preventable. NYTIMES