Residential Greenness and Mortality in a Prospective Cohort of Oldest-Old Women and Men in China

Abstract

Background: Exposure to nature, or greenness, may affect health through several pathways, including health-promoting activities and influencing psychological well-being. How greenness affects old-age health vulnerabilities has not been assessed.Objective: We assessed the relationship between residential greenness and its relationship to mortality in an elderly cohort representative of China.Methods: We used the prospective China Longitudinal Health Longevity Survey (CLHLS) cohort to assess the relationship between greenness and mortality. Our exposure was assessed by satellite derived Normalized Difference Vegetation Index (NDVI) in 250m and 1250m radius around residential addresses between 2000 to 2014 in 3839 women and men. We calculated cumulative, contemporaneous, and change of NDVI values over time. We used all-cause mortality, excluding accidental death, as our outcome measurement.Results: The mean age of our study population at baseline was 92 (sd: 7.57) years. Among 3839 subjects totaling 13253 person-years, we observed 3244 deaths during follow up. We used cox-proportional hazard models, adjusted for age, gender, ethnicity, rural/urban residence, geographical region, education years, occupation before age 60, marital status, smoking status, alcohol consumption, exercise, financial support, and co-residence status. Compared to the lowest quartile of contemporaneous NDVI values, those in the highest quartile had a HR of 0.82 (95% CI: 0.74 – 0.92) for the 250-m radius, and 0.76 (95% CI: 0.69 – 0.85) for the 1250-m radius. No significant effects were not found for cumulative NDVI measurement.Conclusion: In this prospective cohort of older adults, we observed that living in areas with higher levels of greenness was associated with lower levels of mortality. Furthermore, those living in areas of increasing greenness over time also saw a reduction in mortality. Our research has policy implications for eco-civilization and preparing for aging societies in China.