Associations of urban greenness with asthma and respiratory symptoms in Mexican American children

Background: Evidence on the association between residential surrounding greenness (RSG) in urban areas with asthma and asthma symptoms is inconsistent. Objective: To examine the association of RSG with respiratory outcomes in a sample of Mexican American children living in inner-city Chicago, Illinois. Methods: This study is based on parent-reported data on 1915 Mexican American children. We calculated RSG using the normalized difference vegetation index based on satellite imagery within buffers of 100, 250, and 500 m of each child's residence. Multivariable multilevel mixed-effect logistic regression was used to estimate adjusted odds ratios (aORs) for the effect of a 1-interquartile range increase in greenness. Results: In adjusted analyses, a protective effect of greenness within 100 m was observed for lifetime wheezing (aOR, 0.82; 95% CI, 0.69-0.96). Environmental tobacco smoke (ETS) exposure modified the association of RSG with lifetime asthma and current dry cough at night. For all buffer distances, increased greenness was associated with lower odds of lifetime asthma among children with current ETS exposure (100 m: aOR, 0.43; 95% CI, 0.22-0.87; 250 m: aOR, 0.39; 95% CI, 0.18-0.84; 500 m: aOR, 0.48; 95% CI, 0.26-0.90) and lower odds of current dry cough at night among children with perinatal ETS exposure (100 m: aOR, 0.53; 95% CI, 0.31-0.92; 250 m: aOR, 0.55; 95% CI, 0.31-0.98; 500 m: aOR, 0.55; 95% CI, 0.35-0.87). Conclusion: Our results suggest inverse associations of urban greenness with respiratory outcomes, especially in children exposed to ETS. Further research is needed to examine the mechanisms through which RSG may be associated with the risk of asthma and contribute to health. (C) 2018 American College of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.