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Weather extremes may increase the risk for major adverse cardiovascular events, with a more pronounced impact in younger people and those living in rural areas, a study from Eastern Poland found.

Results also indicated that air pollution can compound the risks for these extreme conditions driven by climate change.

“Climate and air pollution should not be treated as separate risk domains,” said Łukasz Kuźma, MD, MPH, PhD, a cardiologist at the Medical University of Białystok in Białystok, Poland, who presented study results at the European Society of Cardiology Preventive Cardiology (EAPC) Congress 2026 in Ljubljana, Slovenia. Kuźma is also the founder and director of the Polish Smog Exposome Research Center.

“In real life, they act together,” Kuźma told Medscape Medical News. “Heat, cold, particulate matter, nitrogen dioxide, ozone, and other exposures can combine to increase cardiovascular risk, particularly in vulnerable populations.”

The study involved a geospatial analysis in the EP-PARTICLES cohort, a population-based dataset of around 8 million residents in Eastern Poland followed from 2011 to 2020. The cohort included 377,373 cardiovascular deaths and 573,538 major adverse cerebrovascular and cardiovascular events (MACCEs).

Cold Snaps Most Risky

Heat waves were associated with a 7.5% increase in MACCE on the day of exposure, Kuźma told attendees. Total mortality also increased by 7.3% and cardiovascular disease (CVD) deaths increased by 9.5% on those days (P < .001).

Cold snaps were associated with a delayed but more sustained increase in MACCE risk — from 4% to 5.9% (P < .001). CVD death also increased from 4.7% to 6.9% and ST-segment elevation myocardial infarction increased from 7.2% to 10.5% over several days after exposure (P < .001 for both).

The study found the relationships between heat waves and MACCE was more pronounced in individuals aged 65 years or younger. Results also showed a similar trend between cold snaps and MACCE, total mortality, and CVD death for those aged 65 years or younger. Cold snaps also appeared to have a greater impact on MACCE in rural areas, Kuźma said.

Compounding Risk of Air Pollution

The researchers analyzed pollutants and found that heat waves remained consistently associated with higher MACCE risk after adjusting for fine particulate matter smaller than 2.5 µm and nitrogen dioxide. Benzo[a]pyrene (B[a]P) was found to have a significant modification effect and a strong interaction with ground-level ozone.

Fine particulate matter, B(a)P, and ozone amplified the impact of extremely cold weather, but nitrogen dioxide did not, Kuźma said.

“The main added value of this analysis is its scale, geographical setting, and integration of multiple environmental dimensions,” Kuźma said. “Many previous studies have examined temperature extremes and cardiovascular outcomes but often focused on single cities, selected outcomes, or isolated exposures.”

This study, he noted, involved an analysis of a large nationwide dataset covering acute hospitalizations and death across Poland, linked with temperature and air-pollution metrics at the municipality level.

“Importantly, the analysis considers both heat waves and cold waves, evaluates temporal changes in these exposures, and explores whether air pollution modifies or amplifies the cardiovascular effects of extreme temperature,” he said. “This makes the study more relevant to real-world climate health risk assessment, where patients are exposed to combined environmental stressors rather than single isolated hazards.”

‘Important Contributors’ to CV Risk

Dinesh Kalra, MD, MBA, chief of cardiovascular medicine at the University of Louisville, Louisville, Kentucky, who led a previous study of air pollution and CVD, said in an interview thatthe Polish study stands out because of its overall size, substantial number of cardiovascular events, and the nature of the pollution in Eastern Poland, a region that still relies on wood for cooking and coal for electricity and industrial uses.

“People have been studying heat waves and climate change for over three decades now and I think, especially in cardiology, there’s an increasing appreciation of these as important contributors to cardiovascular disease risk, especially in certain parts of the world,” he said.

This study is unique because it used geospatial mapping to identify patterns of air pollution and then overlaid that with heat waves and cold snaps to show a “synergistic increase in risk,” Kalra said. “Both of them compound the adverse effects of each other.”

The study was also unique because it included B(a)P, a hydrocarbon that occurs from wood burning and cigarette smoke, among the evaluated pollutants — one that is becoming increasingly relevant as wildfires become more frequent. The finding that cold may be more hazardous than heat for cardiovascular events was also “very interesting,” especially in North America and Europe, Kalra added.

Cardiologists “have to be cognizant of the Air Quality Index. If the Air Quality Index is bad, then tell patients to stay indoors,” he said. “[T]hose messages are not traditionally being given by cardiologists because they’re so busy trying to place stents and fix heart failure medications that they can kind of forget this whole environmental overlay that’s important for patients.”

Kuźma and Kalra reported no relevant financial relationships.

Richard Mark Kirkner is a medical journalist based in Philadelphia.