Extreme temperatures linked with heart disease deaths

December 12, 2022 – Days that are very hot or very cold increased the risk of death among people with cardiovascular diseases, according to a large long-term international study co-authored by experts from Harvard T.H. Chan School of Public Health.

The study, published December 12 in the journal Circulation, found that one in every 100 cardiovascular deaths—from diseases such as ischemic heart disease, stroke, heart failure, or arrhythmia—may be due to extremely hot or cold days. Such temperature extremes are linked with climate change.

Corresponding author of the study was Barrak Alahmad, research fellow in Harvard Chan School’s Department of Environmental Health.

“The decline in cardiovascular death rates since the 1960s is a huge public health success story as cardiologists identified and addressed individual risk factors such as tobacco, physical inactivity, Type 2 diabetes, high blood pressure, and others,” said Alahmad in a press release from the American Heart Association. “The current challenge now is the environment and what climate change might hold for us.”

Researchers analyzed four decades’ worth of data (1979–2019) from more than 32 million cardiovascular deaths in 567 cities in 27 countries. They compared heart-related deaths on the hottest and the coldest 2.5% of days with those deaths on days that had optimal temperatures. They found that, for every 1,000 cardiovascular deaths, there were 2.2 excess deaths (deaths beyond what would have been expected for a particular day) on extremely hot days, and 9.1 excess deaths on extremely cold days. They also found that, among the types of heart diseases, most additional deaths occurred among people with heart failure.

To prevent cardiovascular deaths during days of extreme temperatures, the researchers suggested targeted warning systems and advice for vulnerable people.

Other Harvard Chan School authors of the study included Aaron Bernstein, Antonella Zanobetti, Joel Schwartz, and Petros Koutrakis.

Read the American Heart Association press release: Extremely hot and cold days linked to cardiovascular deaths

Read a HealthDay article: Climate Change’s Extreme Temperatures Could Mean More Heart Deaths