MONDAY, Sept. 2, 2024 (HealthDay News) -- Hospitals see more admissions for heart attacks in the days after cold weather sets in, new research shows.

"Individuals may be particularly vulnerable to acute cardiac events during periods of cold stress," said study lead author Wenli Ni, a postdoctoral research fellow at Harvard University.

Her team presented its findings Sunday in London at the annual meeting of the European Society of Cardiology, and the study was published simultaneously in the Journal of the American College of Cardiology (JACC).

According to background information in an American College of Cardiology news release, prior research has suggested that cold snaps trigger a larger "cardiovascular burden" on the heart than hot temperatures do.

In the new study, Ni's team tracked outcomes for 120,380 people in Sweden's SWEDEHEART registry. They especially looked at hospital admissions during the Swedish cold season (October through March) from 2005 to 2019.

A cold spell was defined as two or more consecutive days where temperatures dipped to lows that were among the coldest 10% of days for the study period.

Rates of hospitalization for all forms of heart attack declined slightly during the first day of a cold snap, but then rose significantly two to six days after a cold spell began, the team found.

These trends didn't change whether it was a first-time heart attack or whether the person had suffered a heart attack before.

The authors believe the initial decline in heart attacks seen during a cold snap may be because folks may decide to stay inside when lower temperatures first set in. However, that behavior isn't sustainable and they venture out in the days after -- exposing themselves to frigid temperatures and a rise in heart risks.

Kai Chen, an associate professor of epidemiology at the Yale School of Public Health and Dr. Khurram Nasir, a professor of cardiology at Houston Methodist, co-authored an editorial accompanying the new study.

They said that as climate change continues to trigger extremes in temperatures, "addressing both ends of the temperature spectrum will ensure our healthcare systems are well equipped to manage and mitigate these challenges" to cardiovascular health.

More information

Find out more about heart attack at the National Institutes of Health.

SOURCE: American College of Cardiology, news release, Sept. 1, 2024