Time Trends of Greenspaces, Air Pollution, and Asthma Prevalence among Children and Adolescents in India

The prevalence of childhood asthma contributes to the global burden of the disease substantially. Air pollution in India has increased. In this study, we examine the associations among greenspaces, air pollution, and asthma prevalence in children and adolescents over a large, diverse population in India. We used state-wide global burden of disease data on asthma from age 0 to 19 years in 2005, 2011, and 2017. For greenspace, we used the normalized differential vegetation index (NDVI), which is the surface reflectance of light during photosynthetic activity. NDVI, air pollutants (PM2.5, PM10, SO2, NO2, and O3), weather, and socio-demographic factors were included in generalized estimating equation (GEE) models to estimate their associations with childhood asthma prevalence over time. Novel data visualization illustrated the complex spatial distributions. NDVI was associated with asthma prevalence (β = 0.144; 95% CI = 0.10, 0.186; p < 0.0001) for high PM2.5, along with high levels of both gaseous air pollutants, SO2, and NO2 ((β = 0.12; 95% CI = 0.08, 0.16; p < 0.0001) and (β = 0.09; 95% CI = 0.05, 0.13; p < 0.0001)). However, NDVI and high O3, had a strong negative association with asthma prevalence (β = −0.19; 95% CI = −0.26, −0.11; p < 0.0001). We observed additional effects of the interaction between the NDVI and high concentrations of PM2.5, PM10, NO2, and O3, assuming that these associations share a common pathway, and found interaction effects for asthma prevalence. Given the changing environmental conditions that interplay over geographical characteristics on the prevalence of asthma, further studies may elucidate a better understanding of these complex associations.