During the summer of 2023, record temperatures scorched many regions of the United States. As expected, emergency department visits for heat-related illnesses also increased during that period, according to the CDC. This worrying trend is expected to continue as climate change causes longer, hotter and more frequent extreme heat events.
People with underlying health problems, particularly cardiovascular disease, are more susceptible to the dangers of high temperatures. Air pollution, another risk to heart health, can also be problematic during the summer months.
Why heat is hard on the heart
People with or at risk for cardiovascular disease should use extra caution when exercising outdoors in hot weather. When temperatures rise, exercise becomes more demanding because the heart has to pump extra blood to both the muscles and skin to help dissipate excess heat. However, when the air temperature approaches body temperature (around 98°F), this cooling process becomes ineffective. Sweating helps cool the body by converting liquid sweat into water vapor, but high humidity levels above 75% make evaporation difficult.
Tips for hot climates
It's still important to exercise during hot weather, but you may need to reduce the intensity. Here are some additional tips for exercising safely during heat waves:
Avoid outdoor activity during the hottest part of the day.: Temperatures typically peak between noon and 3 p.m., so consider exercising early in the morning or early afternoon, away from high-traffic areas.
Choose the right outfit: Wear lightweight, light-colored clothing made of sweat-wicking material to stay cool.
Keep hydrated: Drink water throughout the day, especially when you are active outdoors. For exercise lasting more than an hour, sports drinks are better as they contain electrolytes such as potassium, sodium and magnesium, which replenish what is lost through sweating. People taking blood pressure medications, especially diuretics, should be very careful and drink plenty of water. Exercise in water or air-conditioned spaces:
Air quality concerns
High temperatures during summer accelerate chemical reactions that generate air pollution. Smog and haze result from a combination of dust, water vapor and small airborne particles from industrial power plants, vehicle emissions and forest fires. These fires, which occur more frequently in summer and early fall due to climate change, significantly affect overall air quality.
Air pollution contains invisible particles less than 2.5 microns in diameter, known as PM2.5. These particles are so tiny that they bypass the filters in the nose and upper airways and pass through the lungs into the bloodstream. There, they can interact with receptors and activate nerves that help regulate heart rate and breathing, and also stimulate inflammation, accelerating atherosclerosis (the buildup of fatty plaque inside the arteries).
There is still much to learn about the effects of air pollution on the heart and the best prevention strategies. However, people should heed warnings about staying indoors when air quality is poor and be mindful of when and where they exercise.
When discussing exercise routines with healthcare providers, it is important to consider air quality. For example, running near busy roads during rush hour should be avoided due to higher levels of pollution.
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