Not all farming environments protect against the development of asthma and wheeze in children.
BACKGROUND
In recent years, studies have shown a protective effect of being raised in a farm environment on the development of hay fever and atopic sensitization. Inconsistent data on the relation of farming to asthma and wheeze have raised some doubt about a true protective effect.


OBJECTIVE
We sought to study the differential effects of farm-associated exposures on specific asthma-related health outcomes.


METHODS
The cross-sectional Prevention of Allergy Risk Factors for Sensitization in Children Related to Farming and Anthroposophic Lifestyle study included 8263 school-age children from rural areas in 5 European countries. Information on farm-related exposures and health outcomes was obtained by using questionnaires. In subsamples allergen-specific IgE and RNA expression of CD14 and Toll-like receptor genes were measured, and dust from children's mattresses was evaluated for microbial components.


RESULTS
Inverse relations with a diagnosis of asthma were found for pig keeping (odds ratio [OR], 0.57; 95% CI, 0.38-0.86), farm milk consumption (OR, 0.77; 95% CI, 0.60-0.99), frequent stay in animal sheds (OR, 0.71; 95% CI, 0.54-0.95), child's involvement in haying (OR, 0.56; 95% CI, 0.38-0.81), and use of silage (OR, 0.55; 95% CI, 0.31-0.98; for nonatopic asthma) and in Germany for agriculture (OR, 0.34; 95% CI, 0.22-0.53). Protective factors were related with higher expression levels of genes of the innate immunity. Potential risk factors for asthma and wheeze were also identified in the farm milieu. Levels of endotoxin and extracellular polysaccharides were related to the health outcomes independently of the farm exposures.


CONCLUSIONS
The protective effect of being raised in a farm environment was ascribed to distinct exposures.


CONCLUSIONS
The development of atopic sensitization and atopic and nonatopic asthma is most likely determined by different environmental factors, possibly reflecting distinct pathomechanisms.
Ege
Markus Johannes
MJ
University Children's Hospital Munich, Germany.
Frei
Remo
R
Bieli
Christian
C
Schram-Bijkerk
Dieneke
D
Waser
Marco
M
Benz
Marcus R
MR
Weiss
Gertraud
G
Nyberg
Fredrik
F
van Hage
Marianne
M
Pershagen
Göran
G
Brunekreef
Bert
B
Riedler
Josef
J
Lauener
Roger
R
Braun-Fahrländer
Charlotte
C
von Mutius
Erika
E
D000293:Adolescent; D000383:Agriculture; D000818:Animals; D000829:Animals, Domestic; D001249:Asthma / Q000453:epidemiology* / Q000209:etiology; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D004781:Environmental Exposure; D005260:Female; D015870:Gene Expression; D006801:Humans; D006967:Hypersensitivity / Q000453:epidemiology / Q000209:etiology; D007073:Immunoglobulin E / Q000097:blood; D018950:Lipopolysaccharide Receptors / Q000378:metabolism; D008297:Male; D012135:Respiratory Sounds / Q000209:etiology*; D051193:Toll-Like Receptors / Q000378:metabolism
D018950:Lipopolysaccharide Receptors; D051193:Toll-Like Receptors; D007073:Immunoglobulin E