Modification of Caesarean Section on the Associations between Air Pollution and Asthma in Seven Chinese Cities
24 Pages Posted: 23 Oct 2019More...
Background: It is unknown whether giving birth via caesarean section (c-section) is a modifier for the association between air pollution and asthma.
Methods: From 2012 to 2013, 59,754 children between the ages of 2 and 17 were randomly selected from 94 middle schools, elementary schools and kindergartens in seven Chinese cities for a cross-sectional study. The children's parents or guardians completed questionnaires, from which data on asthma as well as asthma-related symptoms were obtained. Participants' exposure to particles with an aerodynamic diameter ≤1·0μm (PM1), ≤2·5μm (PM2·5), and ≤10μm (PM10) and exposure to nitrogen dioxide (NO2) were estimated using random forest models. We used two-level logistic regressions and added an interaction term between mode of delivery and ambient air pollution into the model to estimate effect modification from c-sections after appropriate adjustments for potential confounding variables.
Findings: Among children delivered by c-section, the adjusted ORs for asthma and its symptoms per 10 μg/m3 air pollutant increase (1·14 95% CI: 1·09-1·19 to 2·10 95% CI: 1·88-2·34) were significantly higher than those of children delivered vaginally (1·04 95% CI: 0·97-1·13 to 1·38 95%CI: 1·23-1·55). The interactions between c-sections and ambient air pollution were statistically significant for all studied respiratory disorders, except current wheeze.
Interpretation: Delivery via c-section appears to increase the risks of air pollution on asthma and its symptoms in our study population of Chinese children.
Funding Statement: This work was supported by the National Natural Science Foundation of China (81872582, 91543208, 81872583, 81673128, and 81703179), the National Key Research and Development Program of China (2018YFE0106900), the Guangdong Provincial Natural Science Foundation Team Project (2018B030312005), the Guangdong Province Natural Science Foundation (2017A050501062, and 2018B05052007), and the Fundamental Research Funds for the Central Universities (19ykjc01).
Declaration of Interests: The authors declare no competing interest.
Ethics Approval Statement: The study was designed and conducted in accordance with the World Medical Association’s Declaration of Helsinki Ethical Principles for Medical Research Involving Human Subjects. The Human Studies Committee of Sun Yat-sen University, Guangzhou, China approved this study. Informed consent was obtained.
Keywords: Caesarean section; air pollution; Asthma; Asthma-related symptom; Effect modification
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