Impacts of cold waves on winter mortality in the Korean Peninsula

This study investigated the impacts of cold waves on winter mortality across the Korean Peninsula using long-term meteorological observations and official mortality records from 2000 to 2023. Direct cold-related deaths were concentrated at lower minimum air temperatures, whereas cardiovascular and respiratory (CVD+Resp) deaths occurred across relatively higher minimum-temperature ranges. Excess mortality increased most prominently one day after the onset of a cold wave, and mortality risk rose nonlinearly when cold-wave duration exceeded four consecutive days. This duration effect was particularly pronounced for CVD+Resp deaths. A Gradient Boosting Machine model was used to quantify the relative contributions and nonlinear effects of meteorological factors. Partial dependence analysis showed that insolation (26.1%) and wind direction (25.9%) had the greatest contributions to mortality variability. Furthermore, two-way interaction analysis demonstrated that mortality risk increased markedly under extreme cold conditions, particularly when minimum air temperature fell below -10°C and coincided with low insolation (≤ 2 MJ m⁻² ), as well as northwesterly or easterly wind regimes. Mortality risk was even greater when minimum air temperature dropped below -15°C in combination with dew-point temperatures ≤ -25°C or diurnal temperature ranges ≥ 15°C. These findings indicate that winter mortality associated with cold waves is influenced not only by air temperature but also by the combined and interacting effects of multiple meteorological factors. The results provide a scientific basis for developing more targeted and evidence-based cold-wave adaptation strategies, supporting climate-resilient health policy and regional vulnerability management.