As summer temperatures soar across the United States, the American Heart Association is raising awareness about the dangerous effects of extreme heat on the cardiovascular system. While hurricanes and tornadoes often dominate headlines, extreme heat is the leading weather-related cause of death in the country, according to the National Weather Service.
A report in the Journal of the American Medical Association found that more than 2,300 people died from heat exposure in the U.S. in 2023. Research published in the American Heart Association’s journal Circulation projects that heat-related cardiovascular deaths could more than double in the coming decades.
“Heat forces the heart to work harder,” said Manesh R. Patel, M.D., FAHA, volunteer president of the American Heart Association and chief of the division of cardiology at Duke Health in Durham, North Carolina. “When your body is trying to cool down, your heart rate increases and your blood vessels expand. For people with heart disease, and even those who are otherwise healthy, that added strain can become dangerous quickly.”
The body relies on sweating to cool itself, which can lead to fluid loss and dehydration. Simultaneously, the heart must pump more blood to regulate body temperature, placing significant stress on the cardiovascular system.
To protect against heat-related illness, the American Heart Association recommends limiting outdoor activity between noon and 3 p.m., when temperatures peak. Wearing lightweight, light-colored clothing, a hat, and sunglasses, along with sunscreen, can help. Staying hydrated by drinking water before, during, and after time outdoors is crucial, while alcohol and caffeinated drinks should be avoided as they can contribute to dehydration. Taking breaks in the shade or a cool indoor space allows the body to recover.
Recognizing symptoms of heat exhaustion early can save lives. Signs include headache, cool and pale skin, a fast but weak pulse, dizziness, fainting, weakness, muscle cramps, nausea, or vomiting. If these occur, individuals should stop physical activity, move to a cooler place, cool down with cold water, and rehydrate. Medical attention may be necessary.
Heat stroke is a medical emergency requiring immediate action. Symptoms include a body temperature above 103°F, hot and red skin, a rapid and strong pulse, confusion, headache, loss of consciousness, or nausea. Anyone experiencing these signs should call 9-1-1 immediately.
Physical activity remains important for heart health, even in summer. Options include walking, swimming, biking, or gardening. However, shifting exercise to early morning or evening hours, or moving workouts indoors to air-conditioned spaces, can reduce risk. More information on staying heart-healthy in the heat is available at heart.org.
