Interactive Effect of Residential Greenness and Air Pollution on Mortality in China

Abstract

PDS 70: Green space, Johan Friso Foyer, Floor 1, August 28, 2019, 1:30 PM - 3:00 PM Background/Aim: Increased air pollution and reduced greenspace have been shown to independently lead to higher mortality. Our study aimed to assess interactive effects of greenspace and air pollution on mortality among Chinese elderly. Methods: We used the 2008 wave of China Longitudinal Healthy Longevity Survey. Our participants were followed up from 2008 to 2014. We used satellite remote sensing to calculate Normalized Difference Vegetation Index (NDVI) in the 500m radius and PM 2.5 concentrations at a 1 km × 1 km grid, around participants’ residential addresses. We measured contemporaneous NDVI, which was NDVI value at the time closest to an event; and cumulative NDVI, which was mean NDVI values over the follow-up period. Cox proportional hazards models were used to estimate the effects of NDVI and PM 2.5 and their interaction on all-cause mortality, controlling for a range of potential confounders. Results and Conclusions 12,943 participants were followed up totaling 48,181 person-years. There were 7454 mortality events from 2008 to 2014. The mean age was 87 years old and 84.6% lived in rural area. The median PM 2.5 concentration was 49 μg/m3 in the 3-year window, median contemporaneous and cumulative NDVI was 0.41 and 0.45. The hazard ratio (HR) for a 10 μg/m3 increase in PM 2.5 was 1.14 (95% CI: 1.09, 1.18), and the HR for each 0.1 unit increase in contemporaneous NDVI was 0.93 (95% CI: 0.89, 0.97). Similar association was not found for cumulative NDVI (HR: 1.08, 95% CI: 1.02, 1.15). The interaction between contemporaneous NDVI and PM 2.5 was 0.99 (p value: 0.016). Our stratified analysis found that participants living in less green area were more vulnerable to lower levels of PM 2.5. Our study suggests that greenspace modifies association between PM 2.5 and mortality, which has important implications for greenness planning and air pollution control.