ENSO-Driven Mortality: A Cross-Country Analysis Using the Modified Lee–Carter Model

Interannual climate variability poses increasing challenges to public health, with many extreme weather events closely linked to anomalous ocean–atmosphere interactions across the Pacific Ocean, Atlantic Ocean, and Indian Ocean. By taking the El Niño–Southern Oscillation (ENSO) in the Pacific as an entry point, this study incorporates the Southern Oscillation index (SOI), Niño3, Niño4, and Niño3.4 indices into the Lee–Carter model, a stochastic mortality forecast model describing population structure and health status under different mortality assumptions to evaluate how ENSO-related climate variability influences mortality rates in populations from four Pacific Rim countries (Australia, Canada, Japan, and the United States of America (USA)) and two regions of China: the Hong Kong Special Administrative Region and Taiwan Province of China. The results indicate that the negative-binomial specification provides the best fit. For Australia, Canada, Japan, and Taiwan Province of China, the model incorporating SOI performs the best, whereas for Hong Kong SAR and the USA, a dualindex specification using Niño3 and Niño4 yields superior performance. The paper concludes with policy recommendations, including prioritizing protection for elderly populations, establishing a dynamic climate–mortality monitoring platform, and developing region-specific disaster prevention strategies.