During the summer of 2023, record-breaking high temperatures scorched many regions of the United States. Unsurprisingly, emergency department visits for heat-related illnesses also increased during that period, according to the CDC. This concerning trend is expected to continue as climate change leads to longer, hotter, and more frequent episodes of extreme heat.
Individuals with underlying health issues, 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 be more cautious when exercising outside in hot weather. When temperatures rise, exercise becomes more demanding because the heart has to pump extra blood to both the muscles and the skin to help dissipate excess heat. However, when the air temperature nears body temperature (around 98°F), this cooling process becomes ineffective. Sweating helps cool the body by turning liquid sweat into water vapor, but high humidity levels above 75% make evaporation more difficult.
Hot-Weather Tips
It's still important to exercise during warm weather, but you may need to lower your intensity. Here are some additional tips for exercising safely during heat waves:
Avoid outdoor activity during the hottest part of the day: Temperatures usually peak between noon and 3 p.m., so consider exercising in the early morning or early evening, away from traffic-heavy areas.
Choose the right attire: Wear lightweight, light-colored clothing made from sweat-wicking material to stay cooler.
Stay hydrated: Drink water throughout the day, especially when active outdoors. For exercise lasting more than an hour, sports drinks are better as they contain electrolytes like potassium, sodium, and magnesium, which replenish what you lose from sweating. People on blood pressure medications, particularly diuretics, should be extra careful to drink plenty of water. Exercise in water or air-conditioned spaces:
On extremely hot days, consider swimming, doing water aerobics, or working out in an air-conditioned fitness center.
Air Quality Concerns
High temperatures during the summer speed up the chemical reactions that create air pollution. Smog and haze result from a combination of dust, water vapor, and tiny airborne particles from industrial power plants, vehicle emissions, and wildfires. These fires, which occur more frequently in the summer and early fall due to climate change, significantly impact 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 filters in your nose and upper airway, passing through your lungs into your bloodstream. There, they can interact with receptors and trigger nerves that help regulate heart rate and breathing, and they also spur inflammation, accelerating atherosclerosis (the buildup of fatty plaque inside the arteries).
Even low levels of air pollution can increase the risk of heart attack, stroke, and irregular heart rhythms. Therefore, it's important to monitor the air quality in your area. Local news often reports this information, and it is available on many weather-based smartphone apps and from the Environmental Protection Agency at AirNow.
There is still much to learn about air pollution's effects on the heart and the best prevention strategies. However, people should heed warnings about staying inside when air quality is poor and be mindful of when and where they exercise.
When discussing exercise routines with healthcare providers, it's important to consider air quality. For instance, running near busy roads during rush hour should be avoided due to higher pollution levels.
