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July 31, 2023

Extreme heat and air pollution doubles risk of a fatal heart attack, study finds

Hot weather and fine particulate matter – like the smoke from the Canadian wildfires – are independently hard on the body. Together, they're even worse

Adult Health Heart Attacks
Heat Waves and Poor Air Quality Jon Tuleya/For PhillyVoice

Exposure to extreme heat and high levels of fine particulate matter in the air doubles the risk of dying from heart attack, according to a recent study. Above, smoke from wildfires in Canada creates a haze in Philadelphia in June 2023.

Philadelphia endured its first heat warning of the summer last week, with temperatures reaching the upper 90s and the heat index making it feel even hotter. Earlier this summer, smoke from the Canadian wildfires lingered for several days, casting a haze over the skyline and making it difficult to breathe. 

Both conditions – extreme heat and air pollution – are independently known to make cardiovascular disease worse. But when they occur at the same time, they appear to be even more taxing on the heart. 

New research suggests that heat waves that are coupled with high levels of fine particulate pollution doubles the risk of dying of a heart attack. Women and older adults are particularly at risk, researchers found.

The study, published by the American Heart Association, analyzed 202,000 heart attack deaths in a Chinese province between 2015 and 2020. Researchers estimated that up to 2.8% of heart attack deaths may be attributed to the combination of extreme heat and fine particulate matter in the air.

Exposure to high heat stresses the cardiovascular system and makes the heart work harder, which can lead to an increased risk of heart attack, irregular heartbeat and heart failure. Particulate matter is easily inhaled and pushed deep into the lungs, where it can irritate the lungs and blood vessels around the heart, leading to similar heart problems. 

The researchers found that the risk of a fatal heart attack was 18% higher during two-day heat waves when the heat index was between 82.6 to 97.9 degrees, increasing with temperature and duration. And it was 74% during four-day heat waves when the heat index was between 94.8 and 109.4 degrees. The heat index captures the combined effect of temperature and humidity on the body. 

Cold spells also were linked to an increased risk of heart attack deaths, but cold days with high levels of fine particulate matter did not increase the risk to the extent that extreme heat and pollution did. Previous research has found that winter weather is more dangerous on the heart than summer weather, because cold temperatures can cause blood vessels to contract, increasing blood pressure and stress on the heart.

"Extreme temperature events are becoming more frequent, longer and more intense, and their adverse health effects have drawn growing concern," said Dr. Yuewei Lieu, an epidemiologist at Sun Yat-sen University in China. "Another environmental issue worldwide is the presence of fine particulate matter in the air, which may interact synergistically with extreme temperatures to adversely affect cardiovascular health. Our findings provide evidence that reducing exposure to both extreme temperatures and fine particulate matter pollution may be useful to prevent premature deaths from heart attack, especially for women and older adults." 

The American Heart Association stresses the importance of reducing exposure to air pollution and reversing the impact of poor air quality in order to improve cardiovascular health and reduce health inequities in historically marginalized communities.

Most heart attacks occur in people with other risk factors like old age, obesity, tobacco use, high blood pressure, high cholesterol, diabetes, stress and an unhealthy diet. People at increased risk are advised to heed warnings about extreme heat and high levels of air pollution. 

The health effects of climate change and rising temperatures have been well-studied. They have been linked to increased seasonal allergies, congenital heart defects, risk of dementia and premature death from natural disasters and extreme weather events, including flash flooding, hurricanes, wildfires and drought, the Washington Post reported. 

Previous research has tied exposure to fine particulate matter — which are the result of fuel combustion from cars and wildfire smoke — to heart disease, stroke and other health issues. 

"Many people don't recognize that this could be life threatening," Dr. Sanjay Rajagopalan, chief of cardiovascular medicine at University Hospitals Harrington Heart and Vascular Institute, told AARP. "Being in an environment where temperatures are regulated is of the utmost importance." 

There are plenty of ways for people to keep themselves safe and protected during heat waves or days with high levels of fine particulate matter in the air. Liu suggests staying inside when weather is extreme, using fans and air conditioners, staying hydrated and installing window blinds to keep indoor temperatures down. 

When air pollution is high, it's important to use air purifiers in the house, wear a mask outdoors, stay clear of busy roadways when walking and choose less strenuous physical activities. People with respiratory illnesses or asthma should be especially cautious, as fine particulate matter has been linked to a higher risk of asthma attacks. 

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