Abstract
Data integration of epidemiologic studies across different geographic regions can provide enhanced exposure contrast and statistical power to examine adverse respiratory effects of early-life exposure to particulate matter <2.5 microns in diameter (PM(2.5)). Methodological tools improve our ability to combine data while more fully accounting for study heterogeneity. METHODS: Analyses included children enrolled in two longitudinal birth cohorts in Boston, Massachusetts, and Mexico City. Propensity score matching using the 1:3 nearest neighbor with caliper method was used. Residential PM(2.5) exposure was estimated from 2 months before birth to age 6 years using a validated satellite-based spatiotemporal model. Lung function was tested at ages 6-11 years and age, height, race, and sex adjusted z scores were estimated for FEV(1), FVC, FEF(25-75%), and FEV(1)/FVC. Using distributed lag nonlinear models, we examined associations between monthly averaged PM(2.5) levels and lung function outcomes adjusted for covariates, in unmatched and matched pooled samples. RESULTS: In the matched pooled sample, PM(2.5) exposure between postnatal months 35-44 and 35-52 was associated with lower FEV(1) and FVC z scores, respectively. A 5 µg/m(3) increase in PM(2.5) was associated with a reduction in FEV(1) z score of 0.13 (95% CI = -0.26, -0.01) and a reduction in FVC z score of 0.13 (95% CI = -0.25, -0.01). Additionally PM(2.5) during postnatal months 23-39 was associated with a reduction in FEF(25-75%) z score of 0.31 (95% CI = -0.57, -0.05). CONCLUSIONS: Methodological tools enhanced our ability to combine multisite data while accounting for study heterogeneity. Ambient PM(2.5) exposure in early childhood was associated with lung function reductions in middle childhood.