Climate extremes may quietly be pushing heart disease rates higher: Study

Heatwaves, cold snaps and heavy rain do more than disrupt your day. They can quietly raise your risk of heart disease, according to a new report in the American Journal of Preventive Medicine.

"Broadly, we found that extreme heat and extreme cold were associated with a higher city-level cardiovascular disease burden across 157 Chinese cities from 2015 to 2020," Linjiang Wei, one of the primary authors of the study and a PhD-level researcher at Xiamen University, told ABC News.

For every day of heat above 100.4 degrees Fahrenheit, the risk of heart disease for an individual increased by about 3%. For every cold day equal to or less than 14 degrees Fahrenheit, the risk also increased, but only slightly, less than 1%. And any day that saw more than about two inches of rain, the risk increased by almost 2%.

"The link between climate change and cardiovascular risk is certainly well studied, with environmental factors that we've previously looked at accounting for at least one in five of the 20 million annual deaths from cardiovascular disease worldwide," said Dr. Jennifer Miao, a cardiologist at Yale School of Medicine and an ABC News Medical Unit fellow.

"I think that it's important for patients and their health care providers to just recognize and acknowledge that environmental risk factors are a major contributing factor for the development of not only cardiovascular disease, but also lung disease, on cancers -- everything," Miao added.

Some groups are more vulnerable than others, the study found.

People younger than retirement age, smokers, those with high BMI or who live in high-ozone or rural areas, were all at greater risk of weather-related cardiovascular issues. Heart disease risk also varied by region, with heat having a stronger impact in eastern areas and cold having a stronger impact in western areas.

The higher number of dangerous weather days brought on by climate change makes these findings especially concerning, the study's authors noted. An estimated 84% of heat wave days between 2020 and 2024 would not have happened without global warming, according to a 2025 Lancet report on health and climate change.

For patients, this means taking extra precautions during periods of unsafe weather, Wei advised.

Wei suggests staying hydrated, avoiding unnecessary exertion while outdoors during those days, maintaining a stable indoor temperature when possible, and keeping medications available. If concerning symptoms develop, seek medical care, he added.

The connection between severe weather events and heart health isn't fully understood, especially how exposure interacts with factors like medications, air conditioning, and underlying health conditions.

However, Wei said that the findings do not mean that a single bad weather day puts your life at risk.

"This does not mean that a single hot or cold day will necessarily cause a cardiovascular event in any one person," he said. "Rather, it suggests that repeated exposure to extreme weather can shift cardiovascular risk upward at the population level in meaningful ways.”

There is ongoing research to better understand how cumulative exposures affect health.

"I think the main practical message is that weather alerts can also be thought of as cardiovascular health alerts, especially for middle-aged and older adults and for people with other risk factors," said Wei.

Megan Still, MD MSE, is a neurosurgery resident at the University of Florida and a member of the ABC News Medical Unit.