Greenspace and children's lung function in China: A cross-sectional study between 2013 and 2015

This study aims to investigate how surrounding greenspace density and proximity were associated with children's lung function. Between 2013 and 2015, spirometry and a parental survey were performed with children from four primary schools in two Chinese cities. Forced expiratory volume in 1 s (FEV₁, L), forced vital capacity (FVC, L), peak expiratory flow rate (PEF, L/s), and forced expiratory flow at 25 % (FEF₂₅, L/s) and 75 % (FEF₇₅, L/s) of FVC were measured. Outdoor surrounding greenspace index incorporated residential, school and commuting greenness and was weighted using assumed daytime hours spent at home and school. Residential proximity to greenspace index was defined as walking distance to nearest park. A total of 913 children (48.7 % female) were included. Overall, an interquartile range (IQR) increase in outdoor surrounding greenspace was associated with decreased FVC (0.06 L, 95%CI 0.01-0.11), but increased FEV₁/FVC (2.03, 1.13-3.04), PEF (0.26 L/s, 0.13-0.39), and FEF₂₅ (0.30 L/s, 0.17-0.42). Residential proximity to greenspace was associated with increased FEV₁ (0.05 L, 0.02-0.08) and FVC (0.04 L, 0.01-0.07) per IQR decrease in distance. Protective effect was significant for children whose parents were less educated and those living in higher road density areas, though interactions were not significant. Structural equation modeling showed that higher level of surrounding greenspace was associated with lower ambient air pollution and in turn with better lung function. Greenspace density and proximity could influence children's lung function differently.