Exposure to environmental microorganisms reduces risk of childhood asthma

January 01, 0001

Exposure to environmental microorganisms reduces risk of childhood asthma

In two cross-sectional studies, these German authors compared children living on farms with those in a reference group with respect to the prevalence of asthma and atopy and to the diversity of microbial exposure. In one study — PARSIFAL (Prevention of Allergy — Risk Factors for Sensitization in Children Related to Farming and Anthroposophic Lifestyle) — samples of mattress dust were screened for bacterial DNA with the use of single-strand conformation polymorphism (SSCP) analyses to detect environmental bacteria that cannot be measured by means of culture techniques. In the other study — GABRIELA (Multidisciplinary Study to Identify the Genetic and Environmental Causes of Asthma in the European Community [GABRIEL

They found: "In both studies, children who lived on farms had lower prevalences of asthma and atopy and were exposed to a greater variety of environmental microorganisms than the children in the reference group. In turn, diversity of microbial exposure was inversely related to the risk of asthma (odds ratio for PARSIFAL, 0.62; odds ratio for GABRIELA, 0.86;). In addition, the presence of certain more circumscribed exposures was also inversely related to the risk of asthma; this included exposure to species in the fungal taxon eurotium (adjusted odds ratio, 0.37) and to a variety of bacterial species, including Listeria monocytogenes, bacillus species, corynebacterium species, and others (adjusted odds ratio, 0.57)."

The authors concluded: "Children living on farms were exposed to a wider range of microbes than were children in the reference group, and this exposure explains a substantial fraction of the inverse relation between asthma and growing up on a farm."

This may be an important explanation of the increase in asthma observed along with urbanization.

For the full abstract, click here.

N Engl J Med 364:701-709, 24 February 2011
© 2011 to the Massachusetts Medical Society
Exposure to Environmental Microorganisms and Childhood Asthma. Markus J. Ege, Melanie Mayer, Anne-Cécile Normand, et al. Correspondence to Dr. Ege: markus.ege@med.uni-muenchen.de

Category: B. Blood/Blood Forming Organs/Immune Mechanisms. Keywords: asthma, children, microorganisms, farms, allery, cross-sectional study, journal watch.
Synopsis edited by Dr Linda French, Toledo, Ohio. Posted on Global Family Doctor 15 March 2011

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