Risk of fatal heart attack may double in heat wave & high fine particulate pollution days
A new study published in the American Heart Association's journal Circulation suggests that the combination of intense heat and high levels of fine particulate pollution may significantly increase the risk of death from heart attacks. The study, which examined over 202,000 heart attack-related deaths in China, found that extreme temperature events are becoming more frequent and severe, raising concerns about their impact on public health.
The researchers conducted a study to assess the impact of extreme temperatures in combination with high levels of fine particulate pollution on heart attack deaths. They analyzed data from 202,678 heart attack-related deaths that occurred in Jiangsu province between 2015 and 2020. Jiangsu has distinct seasons and experiences a wide range of temperatures and pollution levels. The study focused on older adults, with an average age of 77.6 years, where 52% were older than 80 years, and 52% were male. The researchers also considered particulate exposure on the day of each death and the day before.
To evaluate extreme temperatures, the researchers used the daily heat index, which takes into account both heat and humidity. They examined the duration and intensity of heatwaves and cold snaps. For analysis, they compared heart attack deaths during these periods, referred to as case days, with control days that were on the same day of the week in the same month. If a death occurred on a Wednesday, all other Wednesdays in the same month served as control days. High particulate levels were defined as days with an average fine particulate matter level above 37.5 micrograms per cubic meter.
In comparison to control days, the study revealed the following levels of increased risk for fatal heart attacks:
- During 2-day heat waves with heat indexes at or above the 90th percentile (ranging from 82.6 to 97.9 degrees Fahrenheit), the risk was 18% higher, and it further increased with temperature and duration. During 4-day heat waves with heat indexes at or above the 97.5th percentile (ranging from 94.8 to 109.4 degrees Fahrenheit), the risk was 74% higher. Approximately 3.2% (6,417) of the 202,678 observed heart attack deaths occurred during heat waves with heat indexes at or above the 95th percentile (ranging from 91.2 to 104.7 degrees Fahrenheit) for three or more days.
- During 2-day cold snaps with temperatures at or below the 10th percentile (ranging from 33.3 to 40.5 degrees Fahrenheit), the risk was 4% higher, and it increased with lower temperatures and duration. During 3-day cold snaps with temperatures at or below the 2.5th percentile (ranging from 27.0 to 37.2 degrees Fahrenheit), the risk was 12% higher. Approximately 3.1% (6,331) of the 202,678 observed heart attack deaths occurred during cold spells with temperatures at or below the 5th percentile (ranging from 30.0 to 38.5 degrees Fahrenheit) for three or more days.
- The risk was twice as high during 4-day heat waves that had fine particulate pollution levels above 37.5 micrograms per cubic meter. However, days with high fine particulate pollution levels during cold snaps did not show an equivalent increase in the risk of heart attack deaths.
- Overall, women experienced a higher risk of heart attack during heat waves compared to men.
- People aged 80 and older had a higher risk of heart attack during heat waves, cold snaps, or days with high levels of fine particulate pollution compared to younger adults.
The average age of all individuals who died from a heart attack in Jiangsu between 2015 and 2020, including during non-extreme temperature events, was 77.6 years old. Among them, 52.1% were over 80 years old.
The researchers found that the combination of extreme temperatures and high levels of fine particulate pollution (> 37.5 micrograms per cubic meter), according to WHO targets, may be responsible for up to 2.8% of heart attack deaths.
