New data out of Sweden suggest that short-term exposures to colder temperatures may be associated with an increased risk of hospitalization for myocardial infarction (MI). The study, presented at ESC Congress 2024 in London and simultaneously published in JACC, highlight the need for greater understanding of cold-related cardiac risks as climate change continues to result in shifts in weather patterns.

The population-based study of 120,380 Swedish patients admitted to hospitals for MI from 2005-2019 during the cold season of October through March found a decrease of 1-unit in percentile temperature at a lag of 2-6 days was significantly associated with increased risks of total MI, NSTEMI, and STEMI. Cold spells, defined as periods of at least two consecutive days with a daily mean temperature below the 10th percentile of the temperature distribution for each municipality, were also significantly associated with increased risks for total MI, NSTEMI, and STEMI. However, the authors, Wenli Ni, PhD, and Massimo Stafoggia, PhD, et al., noted that lower air temperature and cold spells at a lag of 0-1 days were associated with decreased risks for MI.

The study findings add to the growing body of evidence from other countries like Finland, Germany, China and Vietnam, which have also showed that lower air temperatures or cold spells were associated with increased MI risks.

"As climate change continues to induce complex shifts in regional weather patterns, indirectly subjecting certain areas to further cooling and more temperature variability, the need to enhance protections against common low temperatures and extreme cold to reduce cold-induced cardiac risks may become progressively important," write the authors.

JACC Editor-in-Chief Harlan M. Krumholz, MD, SM, FACC, said the study reveals a crucial link between cold weather exposure and heart attack risk, highlighting a delayed effect that peaks days after the cold spell. "These findings also underscore the urgent need for targeted interventions to protect vulnerable populations during and, particularly, after cold stress," Krumholz said.

In a related editorial comment, also published in JACC, Kai Chen, PhD, and Khurram Nasir, MD, MPH, MSc, FACC, note that the study "provides compelling evidence of the delayed risk of MI following cold exposure, urging us to rethink our strategies and interventions." They add that "addressing both ends of the temperature spectrum will ensure our health care systems are well-equipped to manage and mitigate these challenges, ultimately fostering a more sustainable and resilient cardiovascular future."