Sudden cardiac death in the context of climate change: A 14-year nationwide analysis of extreme weather events

Background Sudden cardiac death (SCD) remains one of the leading causes of cardiovascular (CV) mortality worldwide. Acute environmental stressors, including extreme temperature events, may act as triggers of fatal arrhythmic events, yet population-level data on the impact of heat (HW) and cold waves (CW) on SCD are limited. Purpose This study aims to assess the impact of extreme weather events on SCD in the population of Poland in the context of environmental exposure. Methods A geospatial analysis was conducted for the years 2011-23 on the Polish population. The primary endpoint was SCD. All analyses were conducted using individual-level mortality data. We operationalised temperature extremes at the municipality-day level using the Excess Heat and Cold Factor derived from daily mean temperature from 1991 to 2023 for each of 2257 municipalities. Daily air pollutant exposure data at the municipality level were obtained using the GEM-AQ model. Individual exposure was assigned based on the place of residence. A Poisson pseudo–maximum likelihood regression with high-dimensional fixed effects was used in the analysis. Models were adjusted for long-term temporal trends, day of the week, COVID-19, influenza activity, holidays, atmospheric pressure, and relative humidity. Results are reported as incidence rate ratios (IRRs) with 95% confidence intervals (95% CI). Results Total recorded deaths were 5,386,726 (51.9% male), including 46,173 SCD (63.54% male). HW exposure was associated with increased SCD mortality, with the strongest effects observed at lag 0-2 and a gradual attenuation over the following days. The risk increased by 10% on the day of exposure (lag 0: IRR 1.10; 95% CI: 1.055-1.152) and peaked on lag 1 (IRR 1.13; 95% CI: 1.076-1.83). Conversely, CW were associated with increased SCD mortality, with effects persisting across multiple lag days and showing a more prolonged temporal pattern compared with HW exposure (p<0.001) – Fig. 1. The observed associations remained robust in models that accounted for both temperature extremes and air pollution exposure. HW-related SCD was more pronounced among women and older individuals (p<0.001). No significant effect modification by area of residence (rural/urban) or socioeconomic status was observed. The attributable burden was similar for HW [7405 (1815-15280) years of life lost) and for CW 7596 (1242- 12977)]. Conclusions Both heat and cold waves were associated with an increased risk of sudden cardiac death, with heat effects being more immediate. Together with the comparable attributable burden of both HW and CW underscores the importance of integrating extreme temperature exposure into SCD risk prevention and early warning strategies.