3D walking network shapes social cohesion of the elderly in aging communities: Evidence from Nanjing, China

Vertical development in compact cities profoundly reshapes the daily mobility and accessibility of older adults, thereby altering neighborhood social cohesion (NSC). This study surveyed 852 residents aged 70 years or older across 44 communities in Nanjing, China. NSC was assessed using the self-reported Sampson Scale. Employing three-dimensional (3D) pedestrian distances accounting for vertical displacement, we defined 15-min walkable zones and constructed a 3D NSC network based on modified gravity models. Social network analysis and quadratic assignment procedure (QAP) were applied to examine network structure and its associations with built environment factors. Results revealed that (1) the NSC network displayed a distinct center-periphery structure with power-law distribution; (2) 3D pedestrian distance exerted a significantly stronger negative effect on NSC (β=−0.335, p<0.001) than conventional 2D distance (β=−0.209, p<0.01); and (3) higher building density was positively associated with NSC (β=0.126, p<0.001). These findings demonstrate that traditional 2D accessibility measures underestimate spatial barriers for older adults in high-rise environments and highlight the need to integrate 3D pedestrian accessibility into age-friendly urban planning to sustain social cohesion and support healthy aging in vertically dense cities.