Heart failure (HF) hospitalization risk increases after short-term exposure to cold spells, lower ambient temperatures and higher ambient temperatures, according to a study presented at ESC Congress 2026 and simultaneously published in JACC.

Researchers looked at 482,000 HF hospitalizations in the Swedish National Patient Register between 2006-2021. Cold spells were defined as two or more consecutive days with daily temperatures less than or equal to the 5th percentile (October-March) and heat waves were defined as greater than or equal to the 95th percentile (April-September), using municipality-specific temperature distributions.

Results found cold spells were associated with a higher risk of HF hospitalization within two to six days, reaching statistical significance between three and five days. Lower ambient temperature exposure was associated with a higher risk of hospitalization within three to six days, reaching statistical significance between three to five days.

In other findings, higher temperature exposure was linked to a higher risk of HF over zero to three days. There was no association between heat wave exposure and HF hospitalization.

According to the authors, the delayed risk of hospitalization after cold temperatures and immediate risk seen with hot temperatures underscores the need for time-sensitive management, including monitoring following cold alerts and more urgent response strategies during heat.

“To the best of our knowledge, no previous study has examined the short-term associations between extreme temperature events (cold spells and heat waves) or continuous non-optimal ambient temperatures and [HF] hospitalizations within a Nordic population,” said Wenli Ni, PhD, lead author of the study. “This represents a critical knowledge gap, given that high-latitude settings such as Sweden are characterized by frequent cold exposure while simultaneously facing an emerging, unacclimatized vulnerability to heat as the global climate warms.”

In an accompanying editorial comment, Tiantian Li, PhD, deputy director of the National Institute of Environmental Health, Chinese Center for Disease Control and Prevention in Beijing, warned about continuing to “practice cardiovascular medicine in a meteorological vacuum.”

“The evidence linking non-optimal temperature to cardiovascular harm is now substantial,” said Li. “The scientific mission can no longer rest on accumulating further epidemiological associations alone; it is time to translate these robust data into an actionable early-warning capability.”

The impact of environmental stressors on cardiovascular health was part of a special ESC and JACC Joint Session at ESC Congress 2026, exploring why environmental cardiology has emerged as a critical clinical priority. Speakers examined the cardiovascular impacts of air pollution, wildfire smoke, temperature extremes, and the risks associated with specific PM2.5 constituents and combined environmental exposures. Attendees also gained insight into the latest evidence and practical priorities for research, prevention, and were able to engage with experts like JACC Editor-in-Chief Harlan Krumholz, MD, SM, MACC, around clinical actions needed to address the growing cardiovascular burden of environmental threats.

Visit the JACC Journals at ESC Congress 2026 page to see the full list of simultaneous publications.

Keywords: ESC Congress, ESC26