Exposure to microbial agents in house dust and wheezing, atopic dermatitis and atopic sensitization in early childhood: a birth cohort study in rural areas.
BACKGROUND
Early-life exposure to environmental microbial agents may be associated with development of wheezing and allergic diseases.


OBJECTIVE
To assess the association of microbial exposure in rural homes with the risk of asthma, wheezing, atopic dermatitis and sensitization.


METHODS
Birth cohorts of rural children (n = 1133), half from farmer families, were followed up from birth to 2 years of age by questionnaires in five European centres. Endotoxin and extracellular polysaccharides (EPS) of Penicillium and Aspergillus spp. were determined from living room floor and mother's mattress dust samples collected at 2 months of age. Specific IgE against 19 allergens was measured at 1 year of age. Discrete-time hazard models, generalized estimations equations (GEE) and logistic regression were used for statistical analyses.


RESULTS
The incidence of asthma was inversely associated with the amount of dust (adjusted odds ratio (aOR) 0.73, 95% CI 0.58-0.93) and the loads (units/m(2)) of EPS (aOR 0.75, 95% CI 0.55-1.04) and endotoxin (aOR 0.79, 95% CI 0.60-1.05) in the mother's mattress. Similar associations were seen with wheezing and with living room floor dust. The microbial markers were highly correlated and their effects could not be clearly separated. The inverse associations were seen especially among non-farmers. The risk of sensitization to inhalant allergens increased with increasing endotoxin exposure from mattress dust. No associations were observed with concentrations (units/g) or with atopic dermatitis.


CONCLUSIONS
The amount and microbial content of house dust were inversely associated with asthma and wheezing, but due to high correlations between microbial agents and amount of dust, it was not possible to disentangle their individual effects. New ways to better measure and represent exposure to environmental microbes, including indexes of biodiversity, are needed especially among farmers.
Department of Environmental Health, National Institute for Health and Welfare, Kuopio, Finland. anne.karvonen@thl.fi
A M
AM
Karvonen
A
A
Hyvärinen
U
U
Gehring
M
M
Korppi
G
G
Doekes
J
J
Riedler
C
C
Braun-Fahrländer
S
S
Bitter
S
S
Schmid
L
L
Keski-Nisula
M
M
Roponen
V
V
Kaulek
J-C
JC
Dalphin
P I
PI
Pfefferle
H
H
Renz
G
G
Büchele
E
E
von Mutius
J
J
Pekkanen
D000328:Adult; D000383:Agriculture; D000485:Allergens / Q000032:analysis / Q000276:immunology; D001249:Asthma / Q000453:epidemiology / Q000276:immunology; D001317:Austria / Q000453:epidemiology; D015415:Biomarkers / Q000032:analysis; D015331:Cohort Studies; D003876:Dermatitis, Atopic / Q000453:epidemiology / Q000276:immunology*; D004391:Dust / Q000032:analysis / Q000276:immunology*; D004731:Endotoxins / Q000032:analysis / Q000276:immunology; D004781:Environmental Exposure; D005260:Female; D005387:Finland / Q000453:epidemiology; D005602:France / Q000453:epidemiology; D005858:Germany / Q000453:epidemiology; D006801:Humans; D006969:Hypersensitivity, Immediate / Q000453:epidemiology / Q000276:immunology*; D007073:Immunoglobulin E / Q000097:blood / Q000276:immunology; D007223:Infant; D007231:Infant, Newborn; D011134:Polysaccharides / Q000032:analysis / Q000276:immunology; D011247:Pregnancy; D012135:Respiratory Sounds / Q000276:immunology*; D012424:Rural Population; D011795:Surveys and Questionnaires; D013557:Switzerland / Q000453:epidemiology
D000485:Allergens; D015415:Biomarkers; D004391:Dust; D004731:Endotoxins; D011134:Polysaccharides; D007073:Immunoglobulin E