A study published July 24, 2023, in the American Heart Association’s journal Circulation found that extreme temperatures and higher concentrations of particulate matter in the air increased the risk of heart attack, especially for women and older adults.
It was reported July 27 in the Washington Post.
Women’s Health Research at Yale asked Lisa Freed, MD, the director of Yale’s Women’s Heart and Vascular Program, for help with this headline.
What is the most important heart health “takeaway” from this study?
Dr. Xu and colleagues studied 86.1 million people in Jiangsu province, China from 2015 to 2020. The study population experienced 202,678 fatal heart attacks during that time. The authors demonstrated that exposure to extreme temperature events (both hot and cold) and high levels of fine particle pollution (PM2.5, or particulate matter that is less than 2.5 microns) increase the risk of death from heart attack.
Most importantly, the authors showed that there was a synergistic (or additive) effect between extreme heat and poor air quality. Approximately 2.8% of all deaths from heart attacks in Jiangsu province were attributed to extreme temperature and high levels of pollution, with a disproportionate number occurring on extremely hot days with the highest levels of pollution.
What did the study reveal about women, or the influence of sex and gender, and health outcomes?
The study showed that women had a higher risk of fatal heart attack than men during the extreme temperature events. The authors suggested this may be based on women’s inherent physiology—for example, they have a less robust ability to regulate their internal temperature and a lower sweating capacity than men, which in turn limit their ability to quickly adapt to extreme temperature events.
What are the strengths and limitations of this study?
The greatest strength of this study is the large number of people studied. This adds to the precision and power of the data. In addition, the authors studied apparent temperature rather than air temperature, which reflects human perceived temperature and is a more accurate measure to assess the effect of temperature on people.
Possible limitations include concern over how generalizable the data from the people of Jiangsu province are to the rest of the world. For example, Jiangsu province has a higher pollution level than North America or Europe and a lower one than South Asia. Also, access to health care and access to personal adaptive measures to address heat or pollution vary amongst countries and may affect the relationship between environment and occurrence of heart attack. Sociocultural factors related to the heat are also particularly impactful for women. A recent study found women suffer a higher share of harmful health effects and are still expected to take on a greater share of the household care burden. When factoring for these unpaid work hours, women’s heat related productivity losses increase 260% compared to a 76% increase for men. These additional stressors can increase a woman’s risk for heart attack.
What practical actions, if any, should the public take based on these findings?
The most practical actions are aimed at reducing the risks from extreme heat and high pollution. High temperatures can set off an inflammatory cascade in the body and lead to increased blood clotting, which may lead subsequently to a heart attack. High levels of pollution can also cause inflammation, increased blood clotting, and dysfunction of the lining of the blood vessels that supply the heart.
So, with high heat or pollution, one should:
- Stay inside when it is excessively hot (in the study, the temperatures during the heat waves (three-day) ranged from 32.9-40.4 degrees Celsius or 91.2-104.7 degrees Fahrenheit)
- Hydrate, particularly during hot weather
- Reduce indoor temperatures with blinds, fans, and/or air conditioning
- Monitor air quality forecasts near your home
- Wear an N95 mask outdoors when there is a high degree of pollution or if you are in close proximity to fires
- Use air purifiers to help with indoor pollutants
- Avoid outdoor exercise near highways or where pollution is the greatest
- Opt to exercise indoors during either extreme heat or high levels of pollution
The information provided here may help you make more informed choices. However, it is not a substitute for an individualized medical opinion or diagnosis, and everyone should always consult with their personal physicians to make decisions about their condition or treatment.
