title: Associations of Early Life Exposures and Environmental Factors With Asthma Among Children in Rural and Urban Areas of Guangdong, China.
abstract: BACKGROUND
  Environmental factors may play important roles in asthma, but findings have been inconsistent.
  
  
  OBJECTIVE
  The goal of this study was to determine the associations between early life exposures, environmental factors, and asthma in urban and rural children in southeast China.
  
  
  METHODS
  A screening questionnaire survey was conducted in 7,164 children from urban Guangzhou and 6,087 from rural Conghua. In the second stage, subsamples of 854 children (419 from Guangzhou, 435 from Conghua) were recruited for a case-control study that included a detailed questionnaire enquiring on family history, early life environmental exposures, dietary habits, and laboratory tests (including histamine airway provocation testing, skin prick tests, and serum antibody analyses). House dust samples from 76 Guangzhou families and 80 Conghua families were obtained to analyze levels of endotoxins, house dust mites, and cockroach allergens.
  
  
  RESULTS
  According to the screening survey, the prevalence of physician-diagnosed asthma was lower in children from Conghua (3.4%) than in those from Guangzhou (6.9%) (P < .001). A lower percentage of asthma was reported in rural subjects compared with urban subjects (2.8% vs. 29.4%; P < .001) in the case-control study. Atopy (OR, 1.91 [95% CI, 1.58-2.29]), parental atopy (OR, 2.49 [95% CI, 1.55-4.01]), hospitalization before 3 years of age (OR, 2.54 [95% CI, 1.37-4.70]), high consumption of milk products (OR, 1.68 [95% CI, 1.03-2.73]), and dust Dermatophagoides farinae group 1 allergen (OR, 1.71 [95% CI, 1.34-2.19]) were positively associated with asthma. Living in a crop-farming family at < 1 year of age (OR, 0.15 [95% CI, 0.08-0.32]) and dust endotoxin levels (OR, 0.69 [95% CI, 0.50-0.95]) were negatively associated with asthma.
  
  
  CONCLUSIONS
  Rural children from an agricultural background exhibited a reduced risk of asthma. Early life exposure to crop farming and high environmental endotoxin levels might protect the children from asthma in southern China.
authors.affiliation: Department of Allergy and Clinical Immunology, State Key Laboratory of Respiratory Disease, The First Affiliated Hospital, Guangzhou Medical University, Guangzhou, China.
authors.forename: Mulin
authors.initials: M
authors.lastname: Feng
authors.affiliation: Department of Allergy and Clinical Immunology, State Key Laboratory of Respiratory Disease, The First Affiliated Hospital, Guangzhou Medical University, Guangzhou, China.
authors.forename: Zhaowei
authors.initials: Z
authors.lastname: Yang
authors.affiliation: Department of Allergy and Clinical Immunology, State Key Laboratory of Respiratory Disease, The First Affiliated Hospital, Guangzhou Medical University, Guangzhou, China.
authors.forename: Liying
authors.initials: L
authors.lastname: Pan
authors.affiliation: Research Asia Pacific, ALK A/S, Hong Kong, China.
authors.forename: Xuxin
authors.initials: X
authors.lastname: Lai
authors.affiliation: Department of Allergy and Clinical Immunology, State Key Laboratory of Respiratory Disease, The First Affiliated Hospital, Guangzhou Medical University, Guangzhou, China.
authors.forename: Mo
authors.initials: M
authors.lastname: Xian
authors.affiliation: Department of Allergy and Clinical Immunology, State Key Laboratory of Respiratory Disease, The First Affiliated Hospital, Guangzhou Medical University, Guangzhou, China.
authors.forename: Xiafei
authors.initials: X
authors.lastname: Huang
authors.affiliation: Department of Internal Medicine, Guangdong Pharmaceutical University, Guangzhou, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Chen
authors.affiliation: University Children's Hospital Munich, Department of Pulmonary and Allergy, LMU Munich, Munich, Germany; German Center for Lung Research (DZL), Munich, Germany.
authors.forename: Paul C
authors.initials: PC
authors.lastname: Schröder
authors.affiliation: Department of Environmental Science, University of Eastern Finland, Kuopio, Finland.
authors.forename: Marjut
authors.initials: M
authors.lastname: Roponen
authors.affiliation: University Children's Hospital Munich, Department of Pulmonary and Allergy, LMU Munich, Munich, Germany; German Center for Lung Research (DZL), Munich, Germany.
authors.forename: Bianca
authors.initials: B
authors.lastname: Schaub
authors.affiliation: Department of Paediatrics, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong, China.
authors.forename: Gary W K
authors.initials: GW
authors.lastname: Wong
authors.affiliation: Department of Allergy and Clinical Immunology, State Key Laboratory of Respiratory Disease, The First Affiliated Hospital, Guangzhou Medical University, Guangzhou, China; Guangdong Provincial Key Laboratory of Allergy & Clinical Immunology, Guangzhou Medical University, Guangzhou, China. Electronic address: lijing@gird.cn.
authors.forename: Jing
authors.initials: J
authors.lastname: Li
mesh_terms: D000293:Adolescent; D000383:Agriculture / Q000706:statistics & numerical data*; D000485:Allergens; D000818:Animals; D039741:Antigens, Dermatophagoides; D001249:Asthma / Q000453:epidemiology*; D016022:Case-Control Studies; D002648:Child; D002681:China / Q000453:epidemiology; D003058:Cockroaches / Q000276:immunology; D003611:Dairy Products / Q000706:statistics & numerical data*; D004032:Diet / Q000706:statistics & numerical data*; D004391:Dust / Q000032:analysis; D004731:Endotoxins; D004781:Environmental Exposure / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D006969:Hypersensitivity, Immediate / Q000453:epidemiology; D016015:Logistic Models; D008297:Male; D015999:Multivariate Analysis; D015995:Prevalence; D012424:Rural Population / Q000706:statistics & numerical data*; D012882:Skin Tests; D011795:Surveys and Questionnaires; D014505:Urban Population / Q000706:statistics & numerical data*
chemical_list: D000485:Allergens; D039741:Antigens, Dermatophagoides; D004391:Dust; D004731:Endotoxins
keywords: asthma; endotoxin; environmental factors; house dust mite; rural