Extreme Heat, Fine Particulate Pollution Associated with Fatal Heart Attack Risk

Yuewei Liu, MD, PhD

Credit: American Heart Association

Exposure to extreme temperature events and high fine particulate pollution may double the risk of a fatal heart attack, particularly among women and older adults, according to an analysis of ≥202,000 heart attack deaths in China.¹

Data collected between 2015 - 2020 showed that days with a combination of extreme heat and high levels of fine particulate matter (PM2.5) pollution were associated with the greatest increase in the risk of death from a heart attack.

“Extreme temperature events are becoming more frequent, longer, and more intense, and their adverse health effects have drawn growing concern,” Yuewei Liu, MD, PhD, senior study author and an associate professor of epidemiology in the School of Public Health at Sun Yat-sen University, said in a statement.² “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. However, it remains unknown if and how co-exposure to extreme temperatures and fine particulate pollution might interact to trigger a greater risk of death from heart attack, which is an acute response potentially brought on by an acute scenario and a great public health challenge due to its substantial disease burden worldwide.”

To better understand the impact of extreme temperatures with and without high levels of fine particulate pollution, investigators analyzed 202,678 heart attack deaths in the Jiangsu province between 2015-2020, a region that includes a wide range of temperatures and fine particulate pollution levels over 4 distinct seasons. The deaths generally included older adults, with an average age of 77.6 years (52%, ≥80 years old; 52% male). Investigators collected data on particulate exposure on the day of each death and one day before death.

The team calculated extreme temperatures based on the daily heat index for an area and evaluated both the length and extremeness of heat waves and cold snaps. Then, heart attack deaths (case days) during these periods were compared with control days on the same weekday in the same month. The analysis considered particulate levels as high on any day with an average level of fine particulate matter of ≥37.5 μg per cubic meter.

Upon analysis, Liu and colleagues suggested a reduction in exposure to extreme temperatures and fine particulate pollution could help prevent premature deaths from a heart attack, particularly those in the most vulnerable groups.

When compared with control days, the risk of a fatal heart attack was 18% higher during 2-day heat waves with heat indexes ≥90th percentile (range: 82.6 - 97.9 degrees Fahrenheit) and increased with temperature and duration. Moreover, the analysis showed the risk was 74% higher during 4-day heat waves with heat indexes ≥97.5th percentile (range: 94.8 - 109.4 degrees Fahrenheit). Of the 202,678 observed deaths, data showed 6,417 (3.2%) deaths happened during heat waves with heat indexes ≥95th percentile for ≥3 days.

The analysis also indicated the risk of a fatal heart attack was 4% higher during 2-day cold snaps with temperatures ≤10th percentile (range: 33.3 - 40.5 degrees Fahrenheit), increasing with lower temperature and duration. The risk was 12% higher during 3-day cold snaps with temperatures ≤2.5th percentile (range: 27.0 - 37.2 degrees Fahrenheit). Of the 2020,678 observed heart attack deaths, 6,331 occurred during a cold spell with temperatures ≤5th percentile (range: 30 - 38.5 degrees Fahrenheit) for ≥3 days.

The risk was twice as high during 4-day heat waves that had fine particulate pollution ≥37.5 μg per cubic meter; however, days with high levels of fine particulate pollution during cold snaps did not have an equivalent increase in the risk of heart attack death. Results showed the risk of heart attack death was generally higher among women than men during heart waves and higher among individuals aged ≥80 years during heat waves, cold snaps, or days with high levels of fine particulate pollution.

The team suggested that up to 2.8% of heart attack deaths may be attributable to a combination of extreme temperatures and high levels of fine particulate pollution. In a 2020 scientific statement, the American Heart Association detailed the need to reduce exposure to air pollution and reverse the negative impact of poor air on cardiovascular health, particularly in historically marginalized communities and those with the highest levels of air pollutant exposure.

Liu and colleagues indicated the need for additional research on the potential interactive effects of extreme weather events and fine particulate pollution on heart attack deaths in areas with different temperature and pollution ranges to confirm these findings.

“Strategies for individuals to avoid negative health effects from extreme temperatures 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,” Liu said.² “Using an air purifier in the house, wearing a mask outdoors, staying clear of busy highways when walking, and choosing less-strenuous outdoor activities may also help to reduce exposure to air pollution on days with higher levels of fine particulate pollution. To improve public health, it is important to take fine particulate pollution into consideration when providing extreme temperature warnings to the public.”

References

1. Xu R, Huang S, Shi C, et al. Extreme Temperature Events, Fine Particulate Matter, and Myocardial Infarction Mortality. Circulation. 2023;148(4):312-323. doi:10.1161/CIRCULATIONAHA.122.063504
2. Risk of fatal heart attack may double in heat wave & high fine particulate pollution days. American Heart Association. July 24, 2023. Accessed July 24, 2023. https://newsroom.heart.org/news/risk-of-fatal-heart-attack-may-double-in-heat-wave-high-fine-particulate-pollution-days.