Soaring heat and John Caldwellfine particulate matter in the air may double your risk of heart attack death, according to a new study.

For the study, published in the American Heart Association's journal Circulation on Monday, researchers analyzed more than 200,000 heart attack deaths between 2015 and 2020 in a Chinese province that experiences four distinct seasons and a range of temperatures and pollution levels. 

The findings? Days of extreme heat, extreme cold or high levels of fine particulate matter air pollution were all "significantly associated" with the risk of death from a heart attack — and the greatest risk was seen on days with a combination of both extreme heat and high air pollution levels. Results showed women and older adults were particularly at risk.

"Extreme temperature events are becoming more frequent, longer and more intense, and their adverse health effects have drawn growing concern," senior author Dr. Yuewei Liu, an associate professor of epidemiology in the School of Public Health at Sun Yat-sen University in Guangzhou, China, said in a news release. "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."

Risk of a fatal heart attack was 18% higher during ­2-day heat waves with heat indexes at or above the 90th percentile, ranging from 82.6 to 97.9 degrees Fahrenheit, the study found. The risk was 74% higher during 4-day heat waves with heat indexes at or above the 97.5th percentile, ranging from 94.8 to 109.4 degrees.

During 4-day heat waves with fine particulate pollution levels above 37.5 micrograms per cubic meter, risk was twice as high. For context, the World Health Organization recommends no more than 15 micrograms per cubic meter for more than 3-4 days per year.

Despite their small size of less than 2.5 microns, fine particulates — mostly associated with car exhaust, factory emissions or wildfires — can be inhaled deep into the lungs and irritate the lungs and blood vessels around the heart, the news release explains. 

"Our findings provide evidence that reducing exposure to both extreme temperatures and fine particulate pollution may be useful to prevent premature deaths from heart attack, especially for women and older adults," Liu added.

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In:
• Air Pollution
• American Heart Association
• Heat Wave