高密度建成环境对肺结核发病率的影响机制OA

In high-density cities,the built environment may influence respiratory health by altering exposure to air pollution,yet systematic evidence on the causal chain linking the"built environment-multiple pollutants-tuberculosis(TB),"along with urban-suburban heterogeneity and threshold responses,remains limited.Taking the urban core of Hangzhou as a case study,this study has integrated data on TB incidence,built-environment attributes,and air pollutants(2015-2019)and applies a time fixed-effects model,multiple-mediation analysis,and random-forest modeling to identify overall effects,causal pathways,and nonlinear thresholds.Our results have revealed four main findings.(1)Building density,land-use mix,road-network density,and transport facility density were significantly and positively associated with TB incidence,whereas green spaces(measured by NDVI)showed a significantly stronger protective effect in the central city than in the suburbs.(2)Air pollution served as a critical mediator,accounting for approximately 37％～52％of the total effect of the built environment on TB incidence.Among the six pollutants,PM25 and NO2 dominated the mediating pathways,with their contributions being notably higher in the central city(up to 48％and 32％,respectively)compared to the suburban area(31％and 21％).Moreover,green space exhibited a protective mediated effect by simultaneously reducing the concentrations of multiple pollutants,thereby indirectly lowering the TB risk.(3)Consistent nonlinear relationships were identified.Land-use mix followed a U-shaped curve:the low-risk range of TB incidence was observed between 1.45 and 2.05(Shannon's evenness index),beyond which TB risk increased sharply.Green spaces also showed a U-shaped association,with the optimal health benefit occurring at an NDVI of approximately 0.625;both lower and higher NDVI values were associated with elevated TB incidence.(4)The effect sizes and thresholds were generally higher in the central city than in the suburban areas,indicating a stronger built environment-health linkage in densely built areas.Theoretically,this study extends the explanatory framework for infectious respiratory diseases by explicitly incorporating multiple-pollutant mediation and threshold identification,moving beyond single-pollutant or linear assumptions.Practically,our findings have provided quantitative evidence for zoned and tiered urban planning interventions,including density control,mixed-land-use optimization,green space quality enhancement,and traffic-related pollution mitigation.