title: The effect of infectious burden on the prevalence of atopy and respiratory allergies in Iceland, Estonia, and Sweden.
abstract: BACKGROUND
  Epidemiologic reports on the effect of microbe exposure on the development of atopy and allergic asthma are inconsistent.
  
  
  OBJECTIVE
  The study investigates the association between serologic markers of infections and occurrence of atopy, allergic asthma, and rhinitis among adults in Iceland, Sweden, and Estonia.
  
  
  METHODS
  Individuals (n = 1249; mean age, 42 years) from Iceland, Sweden, and Estonia underwent a structured interview and blood sampling. Specific IgE was measured against 4 allergens, and IgG antibodies were measured against Helicobacter pylori, Toxoplasmosis gondii, hepatitis A virus, herpes simplex virus 1, Chlamydia pneumoniae, EBV, and cytomegalovirus.
  
  
  RESULTS
  Nonatopic subjects more often had positive serology for Helicobacter pylori, herpes simplex virus 1, Chlamydia pneumoniae, and cytomegalovirus. Having a low number (</=3) of IgG antibodies against the various infectious agents was an independent risk factor for atopy (odds ratio [OR], 1.43; 95% CI, 1.06-1.93), allergic asthma (OR, 1.82; 95% CI, 1.12-2.98), and allergic rhinitis (OR, 1.69; 95% CI, 1.21-2.37). The proportion of atopy that can be explained by a lower number (</=3) of infections was 6.7% in Iceland, 9.2% in Estonia, and 16.4% in Sweden, and 6.7%, 48.2%, and 33.4% for allergic asthma, respectively.
  
  
  CONCLUSIONS
  Our data are consistent with cumulative protective effect of infections against atopy and respiratory allergies irrespective of route of infection.
  
  
  CONCLUSIONS
  The study indicates what microbes or combination of microbes play a role in the complex interplay between hygiene and allergy and may contribute toward the understanding of the allergy epidemic.
authors.affiliation: Respiratory Medicine and Allergology, Akademiska Sjukhuset, Uppsala, Sweden.
authors.forename: Christer
authors.initials: C
authors.lastname: Janson
authors.forename: Hulda
authors.initials: H
authors.lastname: Asbjornsdottir
authors.forename: Alda
authors.initials: A
authors.lastname: Birgisdottir
authors.forename: Rúna Björg
authors.initials: RB
authors.lastname: Sigurjonsdottir
authors.forename: María
authors.initials: M
authors.lastname: Gunnbjörnsdottir
authors.forename: Davíd
authors.initials: D
authors.lastname: Gislason
authors.forename: Isleifur
authors.initials: I
authors.lastname: Olafsson
authors.forename: Elízabet
authors.initials: E
authors.lastname: Cook
authors.forename: Rain
authors.initials: R
authors.lastname: Jögi
authors.forename: Thorarinn
authors.initials: T
authors.lastname: Gislason
authors.forename: Bjarni
authors.initials: B
authors.lastname: Thjodleifsson
mesh_terms: D000328:Adult; D000818:Animals; D001249:Asthma / Q000453:epidemiology* / Q000382:microbiology*; D002690:Chlamydia Infections / Q000150:complications / Q000453:epidemiology / Q000276:immunology; D016993:Chlamydophila pneumoniae / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay; D004957:Estonia / Q000453:epidemiology; D005260:Female; D016481:Helicobacter Infections / Q000150:complications / Q000453:epidemiology / Q000276:immunology; D016480:Helicobacter pylori / Q000276:immunology; D006506:Hepatitis A / Q000150:complications / Q000453:epidemiology / Q000276:immunology; D030041:Hepatitis A virus / Q000276:immunology; D006561:Herpes Simplex / Q000150:complications / Q000453:epidemiology / Q000276:immunology; D018259:Herpesvirus 1, Human / Q000276:immunology; D006801:Humans; D006969:Hypersensitivity, Immediate / Q000453:epidemiology* / Q000382:microbiology*; D007055:Iceland / Q000453:epidemiology; D007073:Immunoglobulin E / Q000097:blood; D007074:Immunoglobulin G / Q000097:blood; D007239:Infections / Q000453:epidemiology* / Q000276:immunology; D008297:Male; D015995:Prevalence; D012307:Risk Factors; D016036:Seroepidemiologic Studies; D013548:Sweden / Q000453:epidemiology; D014122:Toxoplasma / Q000276:immunology; D014123:Toxoplasmosis / Q000150:complications / Q000453:epidemiology / Q000276:immunology
chemical_list: D007074:Immunoglobulin G; D007073:Immunoglobulin E