Study: Heart disease deaths linked to extreme temps

Details: Researchers looked at extreme temperature associations of more than 32 million cardiovascular deaths that occurred over 40 years for the study published in the American Heart Association's journal Circulation.

• They built a database of daily counts of specific cardiovascular causes of death — encompassing all CVD causes, ischemic heart disease, stroke, heart failure, and arrhythmia — in 567 cities, 27 countries and across five continents between 1979 and 2019.
• Temperature thresholds for extreme hot and cold days varied in each city analyzed, but were defined by researchers as the top 1% or lowest 1% of the temperature at which the lowest death rate is achieved.

By the numbers: Roughly 11.3 additional deaths out of every 1,000 cardiovascular deaths analyzed were attributed to extreme temperature days, the study found.

• That breaks down as 2.2 additional deaths experienced by heart disease patients on extreme hot days, while 9.1 additional deaths were experienced on extreme cold days.
• This escalating risk applied to multiple common cardiovascular conditions, but was especially pronounced for people with heart failure.
• On extreme hot days, 2.6 additional deaths were experienced by heart failure patients, while 12.8 additional deaths were experienced by heart failure patients on extreme cold days — a respective 12% and 37% greater risk of death compared to moderate climate days.
• In cities like Baltimore, researchers categorized extreme hot and cold temperatures as exceeding 86°F and dropping below 20°F.

Of note: Haitham Khraishah, a co-author of the study and cardiovascular disease fellow at the University of Maryland School of Medicine and University of Maryland Medical Center, told Axios in an email that their work highlights the need for adaptation measures, particularly for "vulnerable individuals with pre-existing cardiovascular diseases."

• "Our study underscores the urgent need to develop measures that will help our society mitigate the impact of climate change on cardiovascular disease," said Khraishah.

The intrigue: Although study authors link the effects of climate change to the extreme temperatures influencing increased mortality rates, winters have warmed in 97% of 238 U.S. locations since 1970, shrinking cold snaps and increasing annual minimal temperatures, according to data by Climate Central.

• Research shows climate change is increasing the frequency and intensity of heat extremes, such as heat waves.

Yes, but: Limitations of the new study include an under-representation of data from South Asia, the Middle East and Africa, which authors acknowledge could be downplaying the overall health impacts of extreme heat.

What they're saying: Sameed Khatana, cardiologist at the Philadelphia VA Medical Center and assistant professor of medicine at the University of Pennsylvania, told Axios in an email that the study expands on prior research.

• "Studies such as this one suggest that as climate change continues to lead to an increase in extreme weather events, the health effects from these events will continue to grow," Khatana, who is not affiliated with the study, said.

The bottom line: "Health care providers, public health leaders, and policy makers need to be aware of this, and efforts to mitigate this, as well as to tackle climate change more broadly, need to be made," Khatana said.