Climate vulnerability factors for temperature-related respiratory mortality: a nationwide two-stage time-series study from 2008 to 2021

BACKGROUND: Taiwan is one of the fastest-warming regions globally. As climate change intensifies, understanding how vulnerability influences health outcomes critical. This study aimed to identify regional vulnerability factors for temperature-related respiratory mortality and effective region-specific adaptation policies. METHODS: A two-stage time-series study was conducted using daily respiratory mortality counts aggregated by county and day. This study employed a distributed lag non-linear model to estimate the temperature-attributable mortality burden from respiratory diseases across all counties and cities in Taiwan. A two-stage meta-analysis was conducted to estimate temperature-mortality associations and quantify cold- and heat-related mortality burdens by county. Meta-regression was used to identify regional vulnerability factors modifying temperature-related mortality risk, and geographically weighted regression (GWR) was applied to characterize the spatial heterogeneity of these effects across counties. RESULTS: Cold exposure was linked to a higher burden of respiratory disease mortality (attributable fraction [AF]: 2.03%, 95% CI: 1.10-2.95) than heat exposure (AF: 1.02%, 95% CI: 0.65-1.40). For cold-related AFs, higher proportions of Indigenous populations (3.27, 0.79-5.75), low-income populations (2.11, 0.67-3.55), greater population density (2.21, 0.46-3.96), and children (0.98, 0.35-1.61) were significantly associated with increased risk, suggesting vulnerability factors. GWR further showed that hospital bed availability had statistically significant protective effects against cold-related AF in 10 of 19 counties (β = - 5.24 to - 6.78), most pronounced in remote mountainous counties (Hualien, Taitung, Kaohsiung). CONCLUSION: Higher proportions of Indigenous populations, low-income population, and children amplify cold-related respiratory mortality. Hospital bed availability confers the strongest protection against cold-related mortality in remote, mountainous counties. Climate adaptation policies for cold-related respiratory health should therefore be tailored to local vulnerability profiles, prioritizing healthcare expansion in geographically remote counties rather than applying uniform investment across all regions.