Abstract
SummaryBackgroundExposure to natural vegetation, or greenness, might affect health through several pathways, including increased physical activity and social engagement, improved mental health, and reductions in exposure to air pollution, extreme temperatures, and noise. Few studies of the effects of greenness have focused on Asia, and, to the best of our knowledge, no study has assessed the effect on vulnerable oldest-old populations. We assessed the association between residential greenness and mortality in an older cohort in China.MethodsWe used five waves (February, 2000–October, 2014) of the China Longitudinal Healthy Longevity Survey (CLHLS), a prospective cohort representative of the general older population in China. We assessed exposure to greenness through satellite-derived Normalised Difference Vegetation Index (NDVI) values in the 250 m and 1250 m radius around the residential address for each individual included in the study. We calculated contemporaneous NDVI values, cumulative NDVI values, and changes in NDVI from the start of the study over time. The health outcome of the study was all-cause mortality, excluding accidental deaths. Mortality rate ratios were estimated with Cox proportional hazards models, adjusted for age, sex, ethnicity, marital status, geographical region, childhood and adult socioeconomic status, social and leisure activity, smoking status, alcohol consumption, and physical activity.FindingsAmong 23 754 individuals (mean age at baseline 93 years [SD 7·5]) totaling 80 001 person-years, we observed 18 948 deaths during 14 years of follow-up, between June, 2000, and December, 2014. Individuals in the highest quartile of contemporaneous NDVI values had 27% lower mortality than those in the lowest quartile for the 250 m radius (hazard ratio [HR] 0·73, 95% CI 0·70–0·76), and 30% lower mortality for the 1250 m radius (0·70, 0·67–0·74). No clear association was observed for cumulative NDVI measurements and mortality. We did not detect an association between area-level changes in NDVI and mortality.InterpretationOur research suggests that proximity to more green space is associated with increased longevity, which has policy implications for the national blueprint of ecological civilisation and preparation for an ageing society in China.FundingBill & Melinda Gates Foundation, US National Institute on Aging, US National Institute of Health, Natural Science Foundation of China, UN Population Fund, China Social Sciences Foundation, and Hong Kong Research Grants Council.
Highlights
Research suggests that exposure to natural vegetation, or greenness, is linked to improved health outcomes
Individuals in the highest quartile of contemporaneous Normalised Difference Vegetation Index (NDVI) values had 27% lower mortality than those in the lowest quartile for the 250 m radius, and 30% lower mortality for the 1250 m radius (0·70, 0·67–0·74)
These published studies on greenness and mortality have been done in regions of the world that have a high human development index, high income per capita, and in populations where people with a higher socioeconomic status live in more desirable areas with more green space
Summary
Research suggests that exposure to natural vegetation, or greenness, is linked to improved health outcomes. Protective associations were seen in the US Nurses Health Study of 108 630 female nurses,[12] in 1·3 million adults aged older than 25 years in Canada,[13] and in 575 000 adults aged older than 35 years in Ontario, Canada.[14] A Swiss national cohort of 4·2 million adults found that residential greenness was associated with reduced risk of mortality independently of other pollution sources.[15] In urban settings, similar associations were observed in 3144 senior citizens in Tokyo, Japan,[16] and in 3556 people aged older than 65 years in Hong Kong.[17] Various systematic reviews have documented the protective effects of green space on mortality.[18,19] These published studies on greenness and mortality have been done in regions of the world that have a high human development index, high income per capita, and in populations where people with a higher socioeconomic status live in more desirable areas with more green space. Whether an association exists between greenness and mortality in middle-income countries remains to be seen
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