Residential Greenness, Asthma, and Lung Function in Young Children

Background. While benefits of greenness to health have been reported, studies specific to child respiratory health are scarce and findings are inconsistent. Objective. Exposure to greenness and respiratory outcomes were examined among the Cincinnati Childhood Allergy and Air Pollution Study (CCAAPS) cohort from birth to age 7 years. Methods. Residential surrounding greenness was averaged using the Normalized Difference Vegetation Index (NDVI) within 200, 400, and 800 meter distances from the home address at birth, age 7 years, and cumulative exposure across childhood (averaged for each year from birth to age 7 years). Respiratory outcomes were assessed at age 7 years, including lung function [percent predicted FEV1 (%FEV1), percent predicted FVC (%FVC), and percent predicted FEV1/FVC (%FEV1/FVC)] and asthma. The associations of a 0.1 unit increase in NDVI with respiratory outcomes were assessed using linear and logistic regression models adjusted for community deprivation, household income, and traffic-related air pollution. Results. Mean NDVI was significantly higher among children without asthma compared to those with asthma at birth in 200 meter and 800 meter distances from the home, and across childhood 200 meters from the home. No relationship was observed between NDVI at any age or buffer distance and asthma after adjustment. NDVI was significantly positively correlated with %FEV1 and %FVC for all distances at age 7 years and across childhood, and at 800 meters at birth. After adjustment, NDVI at age 7 years was significantly associated with %FEV1 (200 meters: β=2.05, 95% CI: [0.08, 3.3]; 400 meters: β=1.64, 95% CI: [0.3, 2.9]) and %FVC (200 meters: β=1.84, 95% CI: [0.7, 3.0]; 400 meters: β=1.55, 95% CI: [0.3, 2.8]; 800 meters: β=1.45, 95% CI: [0.1, 2.8]). No relationship was found between greenness and %FEV1/FVC. Conclusions. Greenness may not increase risk for child asthma, but may be beneficial to concurrent lung function.