Basic and clinical immunologyThe effect of infectious burden on the prevalence of atopy and respiratory allergies in Iceland, Estonia, and Sweden
Section snippets
Study sites and population
The European Community Respiratory Health Survey (ECRHS)–I32 has been a project to study geographical differences in the prevalence and incidence of asthma and atopy and their risk factors in young adults. Individuals age 20 to 44 years were randomly selected during the period 1990 to 1994 from the population of 22 nations at 48 study sites. Interviews were performed and blood samples collected (www.ecrsh.org).
Our study population is composed of all subjects living in Reykjavik, Uppsala, and
Results
There were 1249 subjects included in the study, 595 men and 654 women, of whom 499 were from Reykjavik, 475 from Uppsala, and 275 from Tartu. Mean age was 42.1 ± 7.2 years (Table I). Nonatopic subjects were significantly older and more often smokers than atopic subjects, and they more often had positive serology for H pylori, HSV 1, C pneumoniae, and cytomegalovirus. Nonatopic subjects were also more likely to have a low infectious load of both foodborne and airborne/contact-related microbes (
Discussion
Our study showed that accumulated microbial burden was inversely related to the prevalence of atopy and respiratory allergies in all 3 populations studied. Cumulative effect is indicated by the fact that the atopic/nonatopic prevalence ratio was >1 in subjects with a relatively low microbe load (0-3 microbes), whereas the ratio was <1 in subjects with a high load (4-7 microbes). The high infectious burden protected against atopy, allergic rhinitis, and allergic asthma. Subdivision into
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Supported by Icelandic Research Council grant no. 050405011, the Landspitali University Hospital Research Fund, the Swedish Heart and Lung Foundation, the Vårdal Foundation for Health Care Science and Allergy Research, the Swedish Association Against Asthma and Allergy, and Estonian Science Foundation grant no. 4350.
Disclosure of potential conflict of interest: The authors have declared that they have no conflict of interest.