Heat Waves Can Be Hard on the Heart

When it comes to stroke, studies suggest that extreme temperatures — both hot and cold — can increase risk. What’s more, research presented at the American Stroke Association’s 2020 International Stroke Conference found that spikes in temperatures may influence the severity of strokes. The researchers found that for every 9-degree increase in average temperature range over three days, the severity of strokes increased by 67 percent.

Risks for these heat-related cardiovascular events are not the same for everybody. Precautions are especially important for people with an underlying heart condition, high blood pressure or obesity. Individuals without access to air conditioning and shelter during high-heat days are also at greater risk, Rajagopalan says.

Staying safe in the heat

The takeaway, Rajagopalan says, is to be aware of the risk so you can work to minimize it. “Many people don’t recognize that this could be life threatening,” he says. 

Find a cool place to stick out the hot days — whether it’s at home or at a nearby cooling shelter. (Find them listed by state at the National Center for Health Housing.)

“Being in an environment where temperatures are regulated is of the utmost importance,” Rajagopalan says. What’s more, running your air conditioning during unhealthy air quality days can help to filter out pollutants and reduce the number of harmful particles in the air you breathe.

A few other tips:

Time it. If you have to go out in the heat, try to go out in the early or late parts of the day when the sun isn’t as strong. And don’t be afraid to take regular breaks: Find some shade and rest for a bit. In some areas of the country, the temperatures are high even in the evening. On those days, minimize all of your time outside, Best says.

Stay hydrated. Some people with cardiovascular conditions are used to being told to watch their fluid intake and not overdo it, Harzand says. “But hydration is important,” he adds. People with high blood pressure and heart failure who are fluid-sensitive should talk to their doctors about the best ways to stay hydrated on hot days.

Dress for the heat. Wear lightweight, light-colored clothing, Harzand says. And don’t forget sunglasses, a hat and sunscreen.

Don’t stop taking your medications. “Don’t try and make changes to your medications because you think it’s better or safer to not take a certain medicine when you go outside,” Harzand says. If you have any concerns about your medication regimen and the heat, talk to your doctor.

Be on the lookout for warning signs of heat illness. Older adults are among those at higher risk for heat-related illness. Signs of heat exhaustion include heavy sweating, cold and clammy skin and weakness, among others. Heat stroke symptoms include red, hot and dry skin (no sweating); a fast and strong pulse; confusion, dizziness and nausea; and a throbbing headache.

Editor's note: This story, originally published July 24, 2023, has been updated to reflect new information.