Association of residential greenness exposures on disability: Findings from the cohort study on global AGEing and Adult Health (SAGE) in China.

Background: With the accelerating population ageing globally, disability has become a major public concern. Residential greenness may be one of the influencing factors of disability, but epidemiological evidence in the associations of residential greenness exposures with disability is limited. We aimed to investigate the associations of residential greenness exposures with the risk of disability in the elderly.

Methods: Data of 8408 residents were obtained from the World Health Organization Study on Global AGEing and Adult Health (WHO SAGE) implemented in China during 2007-2018. Participants were matched to the Normalized Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI) at their residential address. Disability was measured by the 12-item Chinese version of the World Health Organization Disability Assessment Schedule (WHODAS 2.0). The associations were examined using a generalized linear mixed model with stratified analyses by the covariates.

Results: We observed significantly negative associations of greenness exposures with the summary WHODAS score [NDVI_500m: -0.290, 95% Confidence Intervals (95%CI): -0.510, -0.070; EVI_500m: -0.453, 95%CI: -0.757, -0.149], and with the score of cognition (EVI_500m: -0.472, 95%CI: -0.881, -0.063), mobility (NDVI_500m: -0.632, 95%CI: -0.965, -0.299; EVI_500m: -0.739, 95%CI: -1.199, -0.280), and participation (NDVI_500m: -0.388, 95%CI: -0.651, -0.125; EVI_500m: -0.530, 95%CI: -0.893, -0.166). People living alone had a more pronounced association in cognition (NDVI_500m: -1.546, 95%CI: -2.471, -0.621). The associations with summary WHODAS score were stronger among participants living in rural areas (NDVI_500m: -0.420, 95%CI: -0.683, -0.157), having less education level (NDVI_500m: -0.618, 95%CI: -0.982, -0.253), and living in northern China (NDVI_500m: -0.381, 95%CI: -0.776, 0.013).

Conclusions: Residential greenness may reduce the onset and worsening of disability, particularly for domains of cognition, mobility, and social participation. Because of its stronger influence among people with low socioeconomic status, increasing greenness levels in areas with lower socioeconomic status may promote health equity.