Heatwaves and air pollution may double fatal heart attack risk

Extreme weather events coupled with high levels of fine particulate air pollution increase the risk of fatal heart attacks, according to a recent study published in Circulation, a journal from the American Heart Association.

The results of the study add to growing concerns over the increasing frequency and intensity of extreme temperature events and the adverse health impacts of air pollution.

Focus of the study

A team of esearchers led by Dr. Yuewei Liu, an associate professor of epidemiology at Sun Yat-sen University, analyzed the details of 202,678 heart attack fatalities from 2015 to 2020 in Jiangsu, a province in China. This province has four distinctive seasons and experiences a broad range of temperatures and pollution levels.

“Extreme temperature events are becoming more frequent, longer, and more intense, and their adverse health effects have drawn growing concern,” said Dr. Liu. 

“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.” 

Studying heatwaves and fatal heart attacks

Dr. Liu further notes that it was crucial to explore the interaction of extreme temperatures and fine particulate pollution in triggering a greater risk of heart attack death. 

As part of their analysis, the researchers considered extreme temperature variations according to the daily heat index, which gauges the combined effect of heat and humidity. They examined both the severity and duration of heatwaves and cold snaps. 

The team then compared the heart attack fatalities during these periods with the heart attack fatalities on control days, which are the same day of the week in the same month.

What the researchers learned 

The findings show a significant increase in the risk of fatal heart attacks during extreme temperature events with high levels of fine particulate pollution (above 37.5 micrograms per cubic meter). Women, older people, and heatwave conditions particularly pronounce this risk.

“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,” said Dr. Liu.

Breaking down the specifics, the researchers found:

• An 18% higher risk of fatal heart attacks during 2-day heatwaves with heat indexes at or above the 90th percentile (82.6 to 97.9 degrees Fahrenheit), increasing with temperature and duration.
  
• A 4% higher risk during 2-day cold snaps with temperatures at or below the 10th percentile (33.3 to 40.5 degrees Fahrenheit), also increasing with lower temperatures and duration.
  
• The risk of a fatal heart attack was twice as high during 4-day heatwaves that had fine particulate pollution above 37.5 micrograms per cubic meter.
  
• The risk was generally higher among women than men during heatwaves.
  
• The risk was higher among people ages 80 and older than in younger adults during heatwaves, cold snaps, or days with high levels of fine particulate pollution.

The researchers further estimated that up to 2.8% of heart attack deaths could be attributed to the combination of extreme temperatures and high levels of fine particulate pollution, aligning with World Health Organization targets.

Mitigation strategies 

Dr. Liu offers suggestions to mitigate the negative health effects of extreme temperatures and air pollution: “Strategies for individuals include following weather forecasts, staying inside when temperatures are extreme, using fans and air conditioners during hot weather, dressing appropriately for the weather, proper hydration, and installing window blinds to reduce indoor temperatures.” 

Dr. Liu also advises using air purifiers indoors, wearing masks outdoors, avoiding busy highways when walking, and choosing less strenuous outdoor activities on high pollution days. These measures are particularly important in regions with historically marginalized and under-resourced communities that bear the brunt of air pollution exposure.

Future research on fatal heart attacks

The experts emphasized the need for further research to confirm their findings and explore the interactive effects of extreme weather and fine particulate pollution on heart attack deaths in different regions with varying temperature and pollution ranges.

Finally, the researchers did not account for any adaptive behaviors individuals may adopt, such as staying indoors or using air conditioning during extreme temperatures or high pollution levels. These adaptations could affect exposure levels and risk patterns, making it a potential area of investigation for future research.

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