title: New risk factors for adult-onset incident asthma. A nested case-control study of host antioxidant defense.
abstract: BACKGROUND
  Host antioxidant defense, consisting of enzymatic antioxidant activity and nonenzymatic antioxidant micronutrients, is implicated in asthma pathogenesis. Studies of antioxidant defense and adult incident asthma have either used measures of antioxidants estimated from questionnaires or not considered enzymatic aspects of host defense.
  
  
  OBJECTIVE
  We conducted the first study designed and powered to investigate the association of antioxidant defenses on adult incident asthma.
  
  
  METHODS
  In a nested case-control study, we followed Shanghai women (aged 40-70 years) without prevalent asthma at baseline, over 8 years. Subjects with incident asthma were ascertained prospectively by gold standard testing of symptomatic women and matched to two asymptomatic control subjects.
  
  
  RESULTS
  Baseline urinary F2-isoprostanes, plasma concentrations of antioxidant micronutrients (tocopherols, xanthines, carotenes, and lycopene), and antioxidant enzyme activity (platelet-activating factor acetylhydrolase [PAF-AH] and superoxide dismutase) were measured from samples collected before disease onset. Among 65,372 women, 150 (0.24%) developed asthma. F2-isoprostane levels before asthma onset were not different between cases and control subjects. Doubling of α-tocopherol concentrations and PAF-AH activity was associated with 50 and 37% decreased risk of incident asthma (α-tocopherol: adjusted odds ratio = 0.52; 95% confidence interval, 0.32-0.84; PAF-AH: adjusted odds ratio = 0.63; 95% confidence interval, 0.42-0.93).
  
  
  CONCLUSIONS
  In this prospective study, α-tocopherol, within normal reference ranges, and PAF-AH enzymatic activity were associated with decreased asthma development. These modifiable risk factors may be an effective strategy to test for primary asthma prevention.
authors.affiliation: 1 Division of Allergy, Pulmonary, and Critical Care Medicine, Department of Medicine.
authors.forename: Emma K
authors.initials: EK
authors.lastname: Larkin
authors.forename: Yu-Tang
authors.initials: YT
authors.lastname: Gao
authors.forename: Tebeb
authors.initials: T
authors.lastname: Gebretsadik
authors.forename: Terryl J
authors.initials: TJ
authors.lastname: Hartman
authors.forename: Pingsheng
authors.initials: P
authors.lastname: Wu
authors.forename: Wanqing
authors.initials: W
authors.lastname: Wen
authors.forename: Gong
authors.initials: G
authors.lastname: Yang
authors.forename: Chunxue
authors.initials: C
authors.lastname: Bai
authors.forename: Meiling
authors.initials: M
authors.lastname: Jin
authors.forename: L Jackson
authors.initials: LJ
authors.lastname: Roberts
authors.forename: Myron
authors.initials: M
authors.lastname: Gross
authors.forename: Xiao O
authors.initials: XO
authors.lastname: Shu
authors.forename: Tina V
authors.initials: TV
authors.lastname: Hartert
mesh_terms: D043203:1-Alkyl-2-acetylglycerophosphocholine Esterase / Q000502:physiology; D000328:Adult; D017668:Age of Onset; D000368:Aged; D000975:Antioxidants / Q000032:analysis*; D001249:Asthma / Q000201:enzymology / Q000209:etiology* / Q000276:immunology; D015415:Biomarkers / Q000097:blood / Q000652:urine; D016022:Case-Control Studies; D002681:China; D028441:F2-Isoprostanes / Q000652:urine; D005260:Female; D006801:Humans; D018977:Micronutrients / Q000097:blood / Q000276:immunology; D008875:Middle Aged; D018384:Oxidative Stress / Q000276:immunology*; D010972:Platelet Activating Factor / Q000502:physiology; D011446:Prospective Studies; D065840:Protective Factors; D012307:Risk Factors; D024502:alpha-Tocopherol / Q000032:analysis / Q000276:immunology*
chemical_list: D000975:Antioxidants; D015415:Biomarkers; D028441:F2-Isoprostanes; D018977:Micronutrients; D010972:Platelet Activating Factor; D043203:1-Alkyl-2-acetylglycerophosphocholine Esterase; D024502:alpha-Tocopherol
keywords: antioxidants; asthma; incidence study; platelet-activating factor acetylhydrolase; α-tocopherol