title: Breastfeeding as a modifier of the respiratory effects of air pollution in children.
abstract: BACKGROUND
  Breastfeeding and air pollution are both important factors for respiratory symptoms and asthma in children. Few studies have examined possible interaction between them on respiratory outcomes.
  
  
  METHODS
  We studied 31,049 Chinese children, ages 2-14 years old, from 25 elementary schools and 50 kindergartens in the Seven Northeastern Cities during 2008-2009. Parents or guardians completed questionnaires about the children's histories of respiratory conditions, risk factors, and feeding methods. Three-year average concentrations of particles with an aerodynamic diameter ≤ 10 µm, sulfur dioxide, nitrogen dioxides, and ozone were calculated from monitoring stations in 25 study districts. We used two-level logistic regressions to examine the effects of exposure, controlling for covariates.
  
  
  RESULTS
  Association of air pollution with childhood respiratory conditions was modified by breastfeeding. Compared with children who had been breastfed, those who were not exhibited consistently stronger effects of air pollution. Among non-breastfed children, odds ratios (ORs) per 10 µg/m increase in nitrogen dioxide were 1.40 (95% confidence interval = 1.19-1.64) for cough, 1.41 (1.16-1.71) for phlegm, 1.17 (1.00-1.36) for current wheeze, and 1.25 (1.07-1.46) for doctor-diagnosed asthma. For breastfed children, the ORs were 1.25 (1.09-1.43) for cough, 1.15 (0.99-1.34) for phlegm, 0.97 (0.87-1.08) for current wheeze, and 1.17 (1.05-1.32) for doctor-diagnosed asthma. Breastfeeding was more protective among younger children. Breastfeeding was also associated with reduced effects of passive smoke exposure in children.
  
  
  CONCLUSIONS
  Breastfeeding is associated with smaller associations between air pollution and respiratory conditions in children, suggesting that breastfeeding reduces susceptibility to the respiratory effects of pollutants.
authors: Department of Biostatistics and Epidemiology, School of Public Health, China Medical University, Shenyang, Liaoning Province, China.
authors: Guang-Hui
authors: GH
authors: Dong
authors: Zhengmin Min
authors: ZM
authors: Qian
authors: Miao-Miao
authors: MM
authors: Liu
authors: Da
authors: D
authors: Wang
authors: Wan-Hui
authors: WH
authors: Ren
authors: Shahida
authors: S
authors: Bawa
authors: John
authors: J
authors: Fu
authors: Jing
authors: J
authors: Wang
authors: Roger
authors: R
authors: Lewis
authors: Alan
authors: A
authors: Zelicoff
authors: Maayan
authors: M
authors: Simckes
authors: Edwin
authors: E
authors: Trevathan
mesh_terms: D000293:Adolescent; D000393:Air Pollutants / Q000009:adverse effects* / Q000032:analysis; D000397:Air Pollution / Q000009:adverse effects* / Q000032:analysis; D001249:Asthma / Q000209:etiology / Q000517:prevention & control*; D001942:Breast Feeding; D002648:Child; D002675:Child, Preschool; D002681:China; D003371:Cough / Q000209:etiology / Q000517:prevention & control*; D003430:Cross-Sectional Studies; D005260:Female; D006306:Health Surveys; D006801:Humans; D019570:Inhalation Exposure / Q000009:adverse effects* / Q000032:analysis; D016015:Logistic Models; D008297:Male; D016017:Odds Ratio; D012135:Respiratory Sounds / Q000209:etiology*; D011795:Surveys and Questionnaires; D014504:Urban Health
chemical_list: D000393:Air Pollutants