How Extreme Heat Affects the Body After 50

A study published July 24 in the journal Circulation found that the risk of a fatal heart attack among older adults in Jiangsu province, China, was higher during two- and four-day heat waves. The most dangerous days, however, were those of extreme heat and high levels of air pollution, including pollution from wildfires. The researchers estimated that up to 2.8 percent of heart attack deaths may be attributed to the combination. 

Dehydration amps up the danger

Hydration plays a major role when it comes to staying healthy in extreme heat. You need fluid to produce the sweat that cools you down; it’s also essential to keeping the cells functioning and the organs running.

But older adults have a harder time staying hydrated, mostly because of a decreased sense of thirst that sets in as you age, says Eric De Jonge, M.D., director of geriatrics at MedStar Washington Hospital Center in Washington, D.C. Certain medications that draw fluid from the body — like diuretics, used to treat high blood pressure and heart failure, and even laxatives — can further complicate matters.

When you’re dehydrated, the kidneys “can spiral into dysfunction,” Bernstein says, kicking off a domino effect of destruction throughout the body. Dehydration is especially risky for the nearly 40 percent of U.S. adults 65 and older who already have kidney disease. Bernstein also urges caution among those who routinely take medications that are hard on the kidneys, including over-the-counter drugs such as ibuprofen.

In addition to kidney disease, another chronic condition that can be worsened by dehydration is diabetes, which the CDC says affects an estimated 29 percent of U.S. adults 65 and older and roughly 19 percent of those ages 45 to 64. Blood sugar becomes more concentrated when there’s less water in the body, the CDC explains, and it becomes “incredibly difficult” to manage blood sugar levels, Bernstein says.

Even the brain feels heat’s effects: The part that’s responsible for long-term planning “goes on vacation,” Bernstein says, “and the part of your brain that is in crisis mode is calling the shots.” Judgment can become impaired and injuries may ensue.

To stay safe, make a plan for high-heat days

With what seems like a never-ending list of health complications that can arise when temperatures rise — add to that list how hot air can aggravate the lungs and trigger breathing issues, even in people who aren’t prone to respiratory distress — experts say a little planning can go a long way when it comes to staying safe during summer.

Here’s what you can do:

Pay attention to humidity. There isn’t a single temperature at which things get dangerous, experts say — so much depends on what an individual is used to and how their body acclimates to heat. But one thing that can ramp up the danger is humidity, since sweat, the body’s cooling mechanism, “doesn’t want to evaporate into air that’s got a lot of water in it already,” Bernstein says.

As a rule of thumb, “85 [degrees] and humid is when we start to really think a lot and talk to our patients and families a lot about preventive measures,” De Jonge says.

Talk to your doctor about your medications. If you take a medication that can affect how your body deals with heat, don’t stop taking it just because high temperatures are on the horizon. “The dangers of stopping may be far worse,” Van Durme warns. Instead, take extra caution in the heat, he says. Your doctor may also decide to switch up your medications during the warmer months.

Drink past the point of thirst — and get creative with hydration. Don’t use thirst as your guide for hydration because “by the time you feel thirsty, you are already significantly dehydrated,” Van Durme says. The color of your urine is a good indicator of whether you’re well hydrated. Thumbs up if it’s a pale yellow; bottoms up if it’s dark yellow or orange, De Jonge says. That’s a sign you need to keep drinking — just not alcohol or caffeine. 

You don’t have to limit yourself to water, though. Cold fruit — think watermelon and cantaloupe — can boost your hydration levels. Mixing in some fruit juice can keep things more interesting for people who get tired of plain water.

Have a fan handy. If you don’t have air-conditioning — or even if you do — fans can help keep you cool by helping sweat to quickly evaporate from the body. But when the temperature is above a certain level, they’re not very helpful. “When the temperature is hotter outside than in our bodies, fans work like a convection oven; we’re actually blowing heat in,” Bernstein says.

A cool shower or bath is another way to cool off at home when things get too warm.

Pay attention to your thermostat. If you have a chronic health condition that could put you at higher risk for heat-related illness and the temperature in your home is over 80 degrees, “you need to do something,” Bernstein says. That might mean turning on a fan, relocating to a cooler level in your home or building, or going to an air-conditioned space, even if it’s a neighbor’s house.

Know your cooling centers. Many communities set up cooling centers during heat waves to provide a safe space for people to cool down. Identify the closest one and make a plan for how you might get there if you need to use it. Also, if you have pets, check to see if they’re welcome, says Diane Garcia-Gonzales, a research scientist with the Fielding School of Public Health at the University of California, Los Angeles, who was part of the team that created community heat maps for California so that residents can stay informed about heat events in their areas.

Don’t forget about other air-conditioned spaces — a church, a library, even a trip to the grocery store or the mall can provide some relief.

Have a backup plan. It’s always good to have a plan in place in case your air-conditioning goes out or your electricity fizzles and your home starts to heat up, Garcia-Gonzales says. Of course, this depends on whether the issue is widespread. If it’s limited, identify a place where you know you and the members of your household can stay cool. And if your air-conditioning goes out during a hot stretch, don’t try to wait out the wave before getting it fixed.

Know the warning signs of heat illness — and what to do. Watch out for confusion and slurred speech. Neurological issues mean you need to get to the emergency room. “That’s the one that you don’t want to mess with,” Van Durme says. If someone just needs to sit down — maybe gets a little woozy but is able to carry on a conversation — get them to cool off by moving them into air-conditioning or positioning them near a fan. And get them to drink.

Another thing: Pay attention to others around you. If you’re at an event or gathering and one person goes down from the heat, “then everybody’s at risk,” Van Durme adds.

Check in on others. Finally, if you have a neighbor, friend or family member who’s at higher risk for heat-related illness, check in on them when things get warm to make sure they’re keeping up their fluids and staying cool and comfortable. “There's no substitute for the human, in-person daily visits,” De Jonge says.

Editor's Note: This story, originally published July 26, 2022, has been updated.