Extreme cold linked to sharp rise in heart-related deaths

On the heels of one of the coldest winters in memory for large swaths of the country, new research highlights an often overlooked cost of cold weather: months with lower temperatures see significantly greater rates of death from heart attacks, strokes and coronary artery disease than milder months. According to a study being presented at the American College of Cardiology's Annual Scientific Session (ACC.26), hotter temperatures were also associated with increases in cardiovascular deaths, but at a more modest rate.

Previous studies have linked temperature extremes with increased cardiovascular mortality, but most research has focused on other countries or on limited portions of the United States. For example, a past study published in JACC found that cold weather exposure was associated with an increased risk of heart attacks. This new study provides the most comprehensive analysis of temperature-related trends to date across a broad swath 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."

Pedro Rafael Vieira De Oliveira Salerno, MD, resident physician at NYC Health + Hospitals/Elmhurst, Icahn School of Medicine at Mt. Sinai, New York, and study's lead author

Researchers analyzed monthly temperatures and total cardiovascular deaths in 819 U.S. locations that collectively include about 80% of the U.S. population over 25 years of age. During the period from 2000-2020, they found that the temperature associated with the lowest rate of cardiovascular death was 23° C (about 74° F), and rates gradually increased as temperatures deviated both below and above that level.

According to the results, cardiovascular death rates followed a lopsided u-shaped curve: both extreme cold and extreme heat were associated with increased mortality, but the rise was steeper and larger on the colder side of the spectrum. The researchers estimate that cold weather accounted for about 40,000 excess cardiovascular deaths each year during the study period (about 6.3% of all cardiovascular deaths), amounting to a total of 800,000 deaths over two decades. By contrast, hot weather accounted for about 2,000 excess deaths each year (about 0.33% of all cardiovascular deaths) or 40,000 deaths over two decades.

Exposure to cold weather triggers a cascade of physiological changes including inflammatory processes and the constriction of blood vessels, which can ultimately lead to a greater risk of adverse cardiovascular events. People who are older or have certain chronic diseases are more vulnerable to these impacts.

"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.

Based on the results, Salerno said that communities should not overlook the dangers of extreme cold as they plan for climate change.

"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 study findings can also provide a useful point of reference for health organizations that may face spikes in health care needs during cold snaps.

"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.

Salerno said that the study is limited by its reliance on monthly, rather than daily, temperature data. In addition, he said that health outcomes were assessed at the population level rather than among individuals. The researchers plan a follow-on study to track associations between temperature and EMS activations related to cardiovascular events.

This study was simultaneously published online in the American Journal of Preventive Cardiology at the time of 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.