Association between residential greenspace exposure and cognitive health in older adults: evidence from Nanjing, China

Amidst global population aging, cognitive function decline among older adults has emerged as a critical public health challenge. Greenspace (GS) may represent an important environmental correlate of cognitive health. Given the restricted mobility of many older adults, their residential environments serve as their primary source of GS. However, conventional research frequently lacks a comprehensive, multidimensional assessment of how residential GS is associated with older adults’ cognitive health, particularly eye-level vegetation and perceived window-view greenery. Therefore, this study examined the associations between objective greenspace exposure (OGE) and perceived greenspace (PG) with cognitive function among older adults. We selected the Mochou Lake sub-district in Nanjing as a representative case study area, initially recruiting 852 older adults across 44 communities, of whom 850 were included in the final analysis. Demographic and PG data were collected via offline surveys, and cognitive function was assessed using the Chinese version of the Montreal Cognitive Assessment-Basic (MoCA-BC). Concurrently, OGE from an eye-level perspective (Green View Index, GVI) was quantified by constructing a high-precision dataset using on-site street view imagery at 30-meter grid intervals. Hierarchical Linear Model (HLM) was employed to examine the associations of OGE, Single-item perceived outdoor greenspace (SPOG), and Single-item perceived window-view greenspace (SPWG) with global cognitive function. Additionally, sensitivity analyses and subgroup analyses were conducted to verify the stability of the results. The results indicated that both SPWG (β = 0.67, p < 0.001) and OGE (β = 0.53, p < 0.001) were positively associated with global cognitive health in older adults, whereas SPOG was not significantly associated. Sensitivity analyses confirmed robust associations of cognitive function and GVI (at 50 m, 100 m, 300 m), OGE, and SPWG, but not for Normalized Difference Vegetation Index (NDVI) or 150 m GVI. No significant GS-income interactions were found. Both OGE and SPWG are positively associated with cognitive function in older adults. These findings highlight the necessity of integrating physical and perceived dimensions in GS assessments. Future age-friendly urban planning should transcend traditional “green quantity” metrics to prioritize visual permeability, everyday visual experiences of nature, and the synergistic enhancement of indoor window views and outdoor social affordances.