District-level solitary death risk assessment incorporating residential environment factors: a hybrid statistical-Delphi model for Seoul, South Korea

Rapid urbanization and population aging in Asian cities have intensified structural conditions underlying solitary death through deteriorating residential environments and weakening community networks. This study develops a district-level indicator system for assessing solitary death risk across Seoul’s 25 districts. Seven key indicators spanning five domains – population structure, residential environment, economic vulnerability, health risk, and social infrastructure – were derived through correlation and regression analysis and validated via expert Delphi survey. Aging housing units (r = 0.727) and the traffic culture index (r = −0.522) were identified as associated built-environment factors. A hybrid weighting approach integrating statistical and Delphi weights at a 50:50 ratio yielded strong within-sample fit (r = 0.854, R2 = 0.729); given the ecological design based on 25 district-level observations, these results reflect internal calibration rather than externally validated predictive accuracy. Jongno-gu and Yongsan-gu were classified as high-risk despite higher income levels, driven by aging housing concentrations – demonstrating that residential environment quality is a significant associated factor beyond economic poverty alone. The findings support spatially targeted housing improvement and community-based prevention strategies at the intersection of architectural planning and public health policy.