Residential greenness attenuated associations of long-term exposure to air pollution with biomarkers of advanced fibrosis

Long-term exposure to air pollutants and residential greenness related to advanced fibrosis have been sparsely studied in low- and middle-income countries. A total of 29883 participants were selected from a cross-sectional survey of the Henan Rural Cohort. Concentrations of air pollutants (particulate matter with an aerodynamic diameter <= 1.0 mu m (PM1), <= 2.5 mu m (PM2.5), <= 10 mu m (PM10) and nitrogen dioxide (NO2)) for participants were predicted by using a spatiotemporal model. Residential greenness of each participant was indicated by Enhanced Vegetation Index (EVI) and Normalized Difference Vegetation Index (NDVI). Independent and joint associations of air pollutants and residential greenness indices with prevalent advanced fibrosis reflected by fibrosis-4 score (FIB4), aspartate-to-platelet-ratio index (APRI) and ALT/AST ratio were analyzed by generalized linear mixed models and their interactive effect on prevalent advanced fibrosis were visualized by using the interplot method. Long-term exposure to PM1, PM2.5, PM10 and NO2 were positively related to FIB4 or APRI as well as prevalent intermediate-high advanced fibrosis; EVI was negatively related to FIB4 or APRI as well as prevalent intermediate-high advanced fibrosis. Negative associations of residential greenness indices (EVI or NDVI) with prevalent advanced fibrosis were decreased as increased air pollutants (PM1, PM2.5, PM10 or NO2) (P < 0.05 for all). This study indicated that residential greenness may partially attenuate negative effect of long-term exposure to air pollutants related to increased prevalent intermediate-high advanced fibrosis, implying that residential greenness may be an effective strategy to reduce the burden of prevalent hepatic fibrosis and its related disease in association with exposure high levels of air pollutants. The Henan Rural Cohort study has been registered at Chinese Clinical Trial Register (Registration number: ChiCTR-OOC-15006699, http://www.chictr.org.cn/showproj.aspx?proj=11375)