Extreme heat and cold are growing cardiovascular risks that can trigger heart attacks, strokes, heart failure and sudden cardiac death, according to a recent scientific statement by experts at Weill Cornell Medicine and other leading institutions. The statement from the American Heart Association, published in Circulation , outlines contributing factors that endanger health and recommendations to mitigate the rising cardiovascular risks posed by extreme temperatures.
Historically, cold weather has caused more cardiovascular deaths because cold days are more frequent. However, the report warns that extreme heat events are increasing in frequency, intensity and duration, which may lead to heat-related deaths outweighing any decline in cold-related mortality. Already, 2024 was the hottest year since the National Oceanic and Atmospheric Administration started record-keeping in 1880.
“As heatwaves increase, we need coordinated action in research, clinical practice and policy to understand how we can keep people safe,” said Dr. Arnab Ghosh , associate professor of medicine at Weill Cornell, and an internist at NewYork-Presbyterian/Weill Cornell Medical Center, who led development of the policy section of the report.
During hot weather, the body cools itself by widening blood vessels and increasing sweating. While this helps release heat, it also lowers blood pressure and reduces body fluid levels. To compensate, the heart beats faster and pumps harder. This can be dangerous for those with cardiovascular disease. Further complicating matters, heart medications, such as diuretics, cause people to lose water. The resulting stress on the heart can bring on a heart attack.
Older adults face some of the highest risks because aging reduces the body’s ability to regulate temperature. Other vulnerable groups include pregnant individuals, infants, outdoor workers and people with low incomes, who often live in areas with limited shade and lack access to air conditioning.
Curbing current and future greenhouse gas emissions would be the best way to limit the role of extreme heat on cardiovascular health, but learning how to live in a hotter world today is also important, Dr. Ghosh said.
The authors emphasize that solutions must operate at multiple levels. The statement suggests, for instance, areas for more research, such as determining the temperature threshold that endangers people at risk of cardiovascular problems and understanding the effects of repeated long-term heat exposure. Another open question is how medications interact with heat stress, especially when a person is taking multiple medications together. “When it’s a hundred degrees outside, should I be adjusting my patients’ medications? Right now, we just don’t know,” Dr. Ghosh said.
Ironically, the health care system is a major contributor to the carbon footprint, accounting for about 8.5% of greenhouse gas emissions in the United States. Everything from the energy needed to run MRI machines to the anesthetics used in operating rooms releases greenhouse gases.
Health care providers can be more conservative about the procedures they recommend and the disposable equipment that they use. But doctors can only change their practices so much without compromising patient safety.
Bringing about meaningful change could require reimagining the entire system, Dr. Ghosh said. For example, more telehealth appointments would reduce carbon emissions from travel to and from appointments. “We need a fundamentally different system that still delivers the same health benefits but is also good for the planet,” he said.
The researchers also highlight the role of policy leaders in helping people deal with heatwaves. This could mean keeping energy costs affordable so people can use their air conditioning, as well as providing cooling centers for people who need a place to cool down.
Meanwhile, planting trees and keeping existing ones healthy helps cool cities. Dr. Ghosh recently published a Nature Communications paper highlighting best practices for urban tree planting. The most effective way to cool cities is not simply to plant more trees, but to create dense, continuous canopies close to homes, streets and public spaces where residents are more exposed.
“Heat is a problem now; we can’t wait,” he said. “We need more tools and creative solutions for protecting people.”
Circulation
Nonoptimal Temperature and Cardiovascular Health: A Scientific Statement From the American Heart Association
26-Mar-2026