Effect of preconceptional, prenatal and postnatal exposure to home environmental factors on childhood pneumonia: A key role in early life exposure

Background: Increasing evidence have associated pneumonia with early exposure to ambient air pollution. However, the role of indoor environmental factors exposure in early life on childhood pneumonia remains unclear. Objective: To examine the association between indoor environmental factors exposure during different timing windows and childhood pneumonia, and to identify the key indoor factor(s) in different critical window(s). Methods: A retrospective cohort study of 8689 pre-schoolers was performed in Changsha, China during 2019-2020. Our questionnaire survey was designed to collect information on pre-schooler's outcome and residential environmental exposure containing indoor pollution and allergens during 1 year before pregnancy, pregnancy, first year, and past year. The associations were further estimated stratified by personal exposure level of outdoor NO2, CO, temperature (T) and different covariates. Associations were assessed by multiple logistic regression model in terms of odds ratio (OR) of 95% confidence interval (CI). Results: Pre-schooler's pneumonia was significantly related with exposure of new furniture, redecoration, mold/ damp stains, and mold or damp clothing or bedding exposure during the four periods, with the strongest associations observed during 1 year before pregnancy based on multi-window model, with ORs (95% CI) of 1.27 (1.12-1.44), 1.26 (1.09-1.46), 1.34 (1.14-1.57), and 1.28 (1.05-1.56) respectively. Environmental tobacco smoke (ETS) including both parental and grandparental smoking were significantly related with increased risk of pre-schooler's pneumonia, and ETS played a more important role in early life, with ORs (95% CI) of 1.17 (1.01-1.36) and 1.19 (1.02-1.39) in pregnancy and first year. Indoor plants particularly nonflowering plants significantly elevated pneumonia risk but only in past year, with ORs (95% CI) of 1.17 (1.05-1.30) and 1.14 (1.03-1.26). Higher pneumonia risk was observed for renovation exposure in pre-birth compared to post-birth, while mold/dampness exerted an accumulative effect with the highest risk for exposure during both pre-and post-birth. Living near traffic road and exposure to high level of traffic-related air pollution and high temperature significantly increased pneumonia risk. Sensitivity analysis found that some sub-groups were more susceptible to pneumonia risk of home environment exposure. Conclusion: Early life exposure to indoor environmental factors plays an important role in pneumonia development, supporting the hypothesis of "Preconceptional and Fetal Origin of Childhood Pneumonia " and "Developmental Origins of Health and Pneumonia ".