title: Endotoxin Exposure: Predictors and Prevalence of Associated Asthma Outcomes in the United States.
abstract: BACKGROUND
  Inhaled endotoxin induces airway inflammation and is an established risk factor for asthma. The 2005-2006 National Health and Nutrition Examination Survey included measures of endotoxin and allergens in homes as well as specific IgE to inhalant allergens.
  
  
  OBJECTIVE
  To understand the relationships between endotoxin exposure, asthma outcomes, and sensitization status for 15 aeroallergens in a nationally representative sample.
  
  
  METHODS
  Participants were administered questionnaires in their homes. Reservoir dust was vacuum sampled to generate composite bedding and bedroom floor samples. We analyzed 7,450 National Health and Nutrition Examination Survey dust and quality assurance samples for their endotoxin content using extreme quality assurance measures. Data for 6,963 subjects were available, making this the largest study of endotoxin exposure to date. Log-transformed endotoxin concentrations were analyzed using logistic models and forward stepwise linear regression. Analyses were weighted to provide national prevalence estimates and unbiased variances.
  
  
  RESULTS
  Endotoxin exposure was significantly associated with wheeze in the past 12 months, wheeze during exercise, doctor and/or emergency room visits for wheeze, and use of prescription medications for wheeze. Models adjusted for age, sex, race and/or ethnicity, and poverty-to-income ratio and stratified by allergy status showed that these relationships were not dependent upon sensitization status but were worsened among those living in poverty. Significant predictors of higher endotoxin exposures were lower family income; Hispanic ethnicity; participant age; dog(s), cat(s), cockroaches, and/or smoker(s) in the home; and carpeted floors.
  
  
  CONCLUSIONS
  In this U.S. nationwide representative sample, higher endotoxin exposure was significantly associated with measures of wheeze, with no observed protective effect regardless of sensitization status.
authors.affiliation: 1 Department of Occupational and Environmental Health, College of Public Health, University of Iowa, Iowa City, Iowa.
authors.forename: Peter S
authors.identifier: http://orcid.org/0000-0002-5045-0929
authors.initials: PS
authors.lastname: Thorne
authors.affiliation: 1 Department of Occupational and Environmental Health, College of Public Health, University of Iowa, Iowa City, Iowa.
authors.forename: Angelico
authors.initials: A
authors.lastname: Mendy
authors.affiliation: 1 Department of Occupational and Environmental Health, College of Public Health, University of Iowa, Iowa City, Iowa.
authors.forename: Nervana
authors.initials: N
authors.lastname: Metwali
authors.affiliation: 2 Division of Intramural Research, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina; and.
authors.forename: Päivi
authors.initials: P
authors.lastname: Salo
authors.affiliation: 3 Social & Scientific Systems, Inc., Durham, North Carolina.
authors.forename: Caroll
authors.initials: C
authors.lastname: Co
authors.affiliation: 3 Social & Scientific Systems, Inc., Durham, North Carolina.
authors.forename: Renee
authors.initials: R
authors.lastname: Jaramillo
authors.affiliation: 3 Social & Scientific Systems, Inc., Durham, North Carolina.
authors.forename: Kathryn M
authors.initials: KM
authors.lastname: Rose
authors.affiliation: 2 Division of Intramural Research, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina; and.
authors.forename: Darryl C
authors.initials: DC
authors.lastname: Zeldin
mesh_terms: D000293:Adolescent; D000328:Adult; D016902:Air Pollution, Indoor / Q000706:statistics & numerical data; D000485:Allergens / Q000276:immunology; D001249:Asthma / Q000453:epidemiology* / Q000276:immunology*; D002648:Child; D004731:Endotoxins / Q000276:immunology*; D005260:Female; D006801:Humans; D007073:Immunoglobulin E / Q000276:immunology; D008297:Male; D015995:Prevalence; D012307:Risk Factors; D014481:United States; D055815:Young Adult
chemical_list: D000485:Allergens; D004731:Endotoxins; D007073:Immunoglobulin E
keywords: allergy; asthma; house dust; indoor air; wheeze