## 5 Discussion  
This study innovatively proposes a spatiotemporal adaptive assessment method, which not only precisely identifies supply-demand imbalances in elderly infrastructure between urban and rural areas but also provides a scientific basis for optimizing existing facilities and selecting new locations. Theoretically, it expands the healthy city theoretical framework, while practically establishing an elderly-friendly urban-rural planning model to facilitate equitable resource allocation, promote social justice, and enhance public well-being, combining both scholarly significance and application value. Leveraging POI data, this study quantifies service accessibility within 5-, 10-, and 15-min walking thresholds around elderly care facilities in Changsha, employing both OLS and GWR models to examine multi-factor impacts on walkability scores. This methodology offers a replicable framework for analyzing existing elderly-oriented service infrastructure in urban and suburban contexts while providing evidence-based guidance for future facility siting. Regarding evaluation metrics for elderly care institutions, prior scholars have established foundational frameworks: [PERSON] et al. [63] developed a composite indicator system for rural Chinese eldercare facilities, revealing spatiotemporal patterns and coupling characteristics of rural nursing home development; [PERSON] et al. [59] assessed service capacity metrics for community-based eldercare facilities. However, existing research lacks a unified evaluation system comparing urban and rural institutional contexts. Addressing this gap, our study conducts a comparative analysis of elderly care facility disparities between urban core areas and township regions. The findings confirm significant accessibility gradients, with urban cores achieving 91.4% service type coverage within 15-min walking circles compared to only 26.86% in townships. This disparity partially reflects the phenomenon of \"excessive reliance on administrative resources in government-driven facility sitting for rural elderly care\". Specifically, spatial weighting analysis reveals that township facility allocation prioritizes government institutions (weight = 0.215), whereas urban areas emphasize lifestyle-supporting amenities such as catering (weight = 0.160). This pattern aligns with [PERSON]'s \"cultural lag\" theory, demonstrating the spatial manifestation of institutional innovation lagging behind demographic aging [30]. Furthermore, the significant negative correlation between sky view factor (SVF) and walking accessibility underscores the inherent conflict between high-density development and open space provision, deepening our understanding of the complex mechanisms shaping built environments. The walkability score in this study, calculated through an enhanced cumulative opportunity approach [76], quantifies comprehensive accessibility to diverse amenities within defined walking catchments. Crucially, this metric exclusively reflects facility diversity and quantity rather than streetscape characteristics. This methodological distinction justifies our regression analysis exploring correlations between walkability performance and both facility-level attributes and streetscape factors. While prior research has examined built environment linkages to 15-min city concepts in Swiss urban contexts [82], our work advances this discourse by systematically quantifying the interplay between streetscape variables and walkability outcomes in Chinese urban cores. These findings inform optimized facility siting strategies and equitable resource allocation frameworks. This study further quantifies the synergistic effects between facility diversity (e.g., 90.37% medical facility coverage in urban 5-min walking zones) and micro-scale street environments (e.g., building space ratio, transportation facility density). Guided by these findings, the optimization of elderly care facility siting provides valuable references for promoting equitable allocation of public resources.