After one of the coldest winters in recent memory across much of the United States, new research is shedding light on a serious and often overlooked danger. Colder months are linked to significantly higher death rates from heart attacks, strokes, and coronary artery disease compared to milder periods. Findings presented at the American College of Cardiology’s Annual Scientific Session (ACC.26) also show that hot weather raises cardiovascular death rates, though the increase is much smaller.
Earlier research has connected extreme temperatures with higher rates of cardiovascular death, but many of those studies focused on other countries or only small parts of the United States. For instance, a prior study in JACC reported that exposure to cold temperatures increased the risk of heart attacks. This latest research offers the most extensive look yet at how temperature affects heart-related deaths across a large portion of the U.S. population.
“This is the first time we have actual numbers for most of the United States, and we found the burden of excess deaths associated with cold is quite substantial,” said Pedro Rafael Vieira De Oliveira Salerno, MD, resident physician at NYC Health + Hospitals/Elmhurst, Icahn School of Medicine at Mt. Sinai in New York, and the study’s lead author.
20 Years of Data Reveal a Clear Pattern
The research team examined monthly temperature data and cardiovascular death rates across 819 locations in the United States, covering about 80% of Americans over age 25. Looking at data from 2000-2020, they identified 23°C (about 74°F) as the temperature associated with the lowest rate of cardiovascular deaths. As temperatures moved higher or lower than this point, death rates increased.
The relationship followed a lopsided u-shaped curve: both extreme heat and extreme cold raised the risk of death, but the effect was much stronger on the cold side. Researchers estimate that cold temperatures contributed to about 40,000 additional cardiovascular deaths each year during the study period (about 6.3% of all cardiovascular deaths), totaling around 800,000 deaths over two decades. In comparison, hot temperatures were linked to roughly 2,000 extra deaths annually (about 0.33% of all cardiovascular deaths), or about 40,000 over the same time frame.
Why Cold Weather Strains the Heart
Cold exposure sets off a chain reaction in the body, including inflammation and narrowing of blood vessels. These changes can increase the likelihood of serious cardiovascular events. Older adults and people with chronic conditions are especially at risk.
“As rates of chronic conditions like diabetes, heart failure and chronic kidney disease rise in the United States, we can expect to see a rise in the number of people who are more vulnerable to the effects of extreme temperatures,” Salerno said.
Planning for Climate and Public Health Risks
The findings suggest that communities should pay closer attention to the dangers of cold weather when preparing for climate-related health risks.
“We tend to focus on heat-related impacts of climate change, but climate change also includes extreme cold. We need to not only have heat-related mitigation measures, but also cold-related mitigation measures,” he said.
The results may also help hospitals and emergency services prepare for spikes in demand during colder periods.
“It’s important for public health planning and also for institutions to anticipate more emergency medical service calls and in-hospital mortality during cold periods. Our systems need to be prepared for that influx of patients,” Salerno said.
Study Limitations and Next Steps
The researchers note that the study used monthly temperature data rather than daily measurements, and outcomes were analyzed at the population level rather than for individuals. Future work will examine how temperature changes relate to emergency medical service activations tied to cardiovascular events.
The study was published online in the American Journal of Preventive Cardiology at the time of its presentation.
Salerno will present the study, “County-Level Temperature-Attributable Cardiovascular Disease Mortality in the U.S.,” on Monday, March 30, at 9:30 a.m. / 14:30 UTC at the Engage Stage for the Young Investigators Award Competition.
ACC.26 will take place March 28-30, 2026, in New Orleans, bringing together cardiologists and cardiovascular specialists from around the world to share the newest discoveries in treatment and prevention.
