Assessing the health burden of climate change in Poland: temperature extremes, air pollution, acute hospital admissions, and mortality over the years 2011-2020

Introduction Climate change is increasingly recognized as a major public-health threat, shifting the distribution of temperature exposure. At the same time, air pollution remains a key, often co-occurring environmental hazard that may amplify temperature-related health risks. Aim To comprehensively assess the acute health impacts of adverse climate-related temperature extremes, including both heatwaves (HW) and coldwaves (CW), and to evaluate how co-exposure to air pollution may modify these associations. Methods A geospatial analysis was performed in the EP-PARTICLES cohort including residents of eastern Poland (N=8,077,671). Data on acute hospitalizations and all cause deaths from 2011–2020 were obtained from the National Health Fund. HW and CW events were indexed using the Excess Heat/Cold Factor at the level of 655 counties. Panel negative binomial regression models were applied to daily events in a county × day structure with air pollution as a modelling variable. The primary endpoint (MACCE) comprised CVD death, STEMI, and ischemic stroke. Results were presented as the percentage increase in admissions (%IR) with 95% confidence intervals (95% CI). Results We recorded 831,246 deaths, including 377,373 CV deaths. The primary MACCE endpoint comprised 573,538 events (median age 79 [68–86], 52.8% men). HW were associated with an increase in MACCE incidence on the day of exposure by +7.5%, AF 3.6%, total mortality (TM) by +7.3%, and CVD deaths by +9.5%/. CW produced a delayed and more sustained increase in the risk of MACCE (from 4% to 5.9%), CVD mortality (from 4.7% to 6.9%), and STEMI (from 7.2% to 10.5%), over several days after exposure (p<0.001 for all). The HW effect (RIRR=1.026; p=0.003) on MACCE was more pronounced in individuals aged <65 years, similarly AF (RRR=1.078; p=0.02). The CW effect was likewise more pronounced in those aged <65 years (MACCE RRR=1.065; TM 1.055; CVD 1.108; all p<0.001). Moreover, CW showed a greater impact on MACCE in rural areas (RRR=1.033; p=0.04). In two-pollutant models, HW remained consistently associated with higher MACCE risk after adjustment for PM2.5 or NO2 (IRR 1.069 and 1.074, respectively), with significant effect modification by B[a]P (p=0.030) and a strong interaction with O3 (p<0.001). CW also increased MACCE (IRR 1.040; p<0.001), but their impact was significantly amplified by PM2.5, B[a]P, and O3, while NO2 showed no interaction. Conclusion Both HW and CW were associated with significant increases in MACCE and mortality, with distinct temporal patterns - heat exerting an immediate impact, and cold producing sustained risk elevations over subsequent days. These effects were more pronounced in younger adults and in rural areas. HW associations with MACCE were robust to adjustment for most air pollutants, whereas cold-wave effects were significantly strengthened by PM2.5, B[a]P and O3, highlighting combined climate–pollution hazards and the need for targeted prevention in vulnerable groups.For image description, please refer to the figure legend and surrounding text.