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Abstract
Household air pollution exposure is a risk factor for obstructive lung diseases. We assessed whether early-life exposure to air pollution during rapid lung growth and development is associated with reduced lung function at age 3. The Household Air Pollution Intervention Network trial randomized 800 pregnant women (9-19 weeks gestation) to a cooking intervention with liquefied petroleum gas or to continue cooking with open fire until the child was 1 year old. We measured 24-hour exposure to particulate matter with aerodynamic diameter 2.5 μm (PM2.5), black carbon (BC), and carbon monoxide (CO) before and during (24-28 and 32-36 weeks of gestation) the trial. Pregnancy exposure was estimated as the time-weighted average of the 24-hour exposures. At age 3, we assessed lung function using oscillometry at frequencies ranging from 7 to 41 Hertz. Outcomes were resistance and reactance at 7 Hertz, area of reactance, resistance at 19 Hertz, resistance difference at 7 and 19 Hertz, and, as exploration, resistance across frequencies. We evaluated the reliability and validity of oscillometry subjected to standard or investigator-proposed quality control using intraclass correlation coefficients (ICC), the effect of the intervention using linear regression, and the causal effect of prenatal exposure leveraging the exposure distribution of children in the trial arms. We obtained oscillometry in 554 children, most missing is explained by uncooperative children. The ICCs of oscillometry subjected to alternative quality control against the reference method or a retest were higher or equal to the ICCs of oscillometry subjected to standard quality control. We found no evidence of an effect of air pollution exposure on oscillometry at age 3 with any of the pre-specified outcomes; however, we found evidence when pooling resistance across frequencies, our exploratory outcome. In a population from a randomized gas cooking trial during pregnancy and infancy in Guatemala, neither the intervention nor the level of pollution exposure was associated with pre-specified lung function outcomes at age 3. The study of lung function trajectories and confirmation of exploratory findings is warranted.