Residential green space structures and mortality in an elderly prospective longitudinal cohort in China

Abstract

Greenness is beneficial to health and is associated with lower mortality. Many studies used the normalized difference vegetation index (NDVI) to measure greenness. However, NDVI cannot be used to indicate landscape type. To go beyond NDVI, we aim to study the association between greenness structures and all-cause mortality of older adults using the 2008–2014 waves of Chinese Longitudinal Healthy Longevity Survey. We calculated landscape indices to quantify three greenspace structure characteristics: area-edge, shape, and proximity. The health outcome was all-cause mortality. We used the Cox-proportional hazards model, adjusted for the study entrant year, age, sex, activities of daily living (ADL), marital status, geographic region, urban or rural residential location, literacy, annual household income, smoking, alcohol and exercise status, biodiversity, numbers of hosts for zoonosis, contemporaneous NDVI, annual average temperature, and 3 year average PM2.5. Among 12 999 individuals (average age at baseline 87.2 years, 5502 males), we observed 7589 deaths between 2008 and 2014. We did not find a consistent dose-response relationship between greenspace structures and all-cause mortality. However, there were some signals of associations. Compared with individuals living in the lowest quartile of the number of patches, the adjusted-hazard ratio (95% CI) of those in the highest quartile was 0.85 (0.80–0.92). In stratified analyses, the largest patch index and perimeter-area ratio had protective effects on males, individuals aged <90, those free of ADL disability, and with higher income. The protective influence of greenspace structures was not as evident compared to NDVI.