More People Die of Heart Attacks When Heat, Pollution Spike

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July 25, 2023 – A new study suggests 3 of every 100 people who die of heart attacks may have survived if they had not been impacted by high levels of air pollution during a heat wave.

The findings were published Monday in the journal Circulation. The study examined weather, air quality, and health data in a single province in China that has four distinct seasons and varying levels of air pollution. The researchers defined extreme heat in terms of a heat index, which is a combination of temperature and humidity. 

Health experts have long known about the increased risk of heart attacks during hot weather. The researchers sought to better understand how many heart attack deaths occur during hot weather, and also how air pollution from fine particulate matter impacts those risks. Fine particulate matter typically comes from car exhaust, factory emissions, or wildfires and can be inhaled deep into the lungs, ultimately impacting blood vessels around the heart. 

The risk of heart attack deaths increased in step with increasing temperatures, duration of the heat wave, and increasing air pollution levels. For example, the risk of heart attack deaths:

  • Increased 18% during 2-day heat waves when the heat index rose above 82 F. 
  • Increased 74% during 4-day heat waves when the heat index rose above 94 F.

Those risks as much as doubled when a heat wave coincided with high levels of fine particulate matter in the air.

Women and older people faced the greatest risk of heart attack death from the dual threats of extreme heat and spiking levels of fine particulate matter in the air. The findings are especially timely as parts of the U.S. grapple with record heat and with dangerous air quality levels from Canadian wildfires.

“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,” researcher Yuewei Liu, MD, PhD, an associate professor of epidemiology in the School of Public Health at Sun Yat-sen University in Guangzhou, China, said in a statement.

Liu said that during extreme heat, people should monitor weather forecasts, stay inside, use fans and air conditioners, dress for the weather, drink enough water, and use window blinds and shades to reduce indoor temperatures. During days when fine particulate matter levels spike, people should use air purifiers indoors, wear masks outdoors, avoid being outdoors near busy highways, and choose less strenuous outdoor activities.