Early-life exposure to environmental microbial agents may be associated with development of wheezing and allergic diseases.
To assess the association of microbial exposure in rural homes with the risk of asthma, wheezing, atopic dermatitis and sensitization.
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.
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.
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.
Western lifestyle is associated with high prevalence of allergy, asthma and other chronic inflammatory disorders. To explain this association, we tested the 'biodiversity hypothesis', which posits that reduced contact of children with environmental biodiversity, including environmental microbiota in natural habitats, has adverse consequences on the assembly of human commensal microbiota and its contribution to immune tolerance.
We analysed four study cohorts from Finland and Estonia (n = 1044) comprising children and adolescents aged 0.5-20 years. The prevalence of atopic sensitization was assessed by measuring serum IgE specific to inhalant allergens. We calculated the proportion of five land-use types--forest, agricultural land, built areas, wetlands and water bodies--in the landscape around the homes using the CORINE2006 classification.
The cover of forest and agricultural land within 2-5 km from the home was inversely and significantly associated with atopic sensitization. This relationship was observed for children 6 years of age and older. Land-use pattern explained 20% of the variation in the relative abundance of Proteobacteria on the skin of healthy individuals, supporting the hypothesis of a strong environmental effect on the commensal microbiota.
The amount of green environment (forest and agricultural land) around homes was inversely associated with the risk of atopic sensitization in children. The results indicate that early-life exposure to green environments is especially important. The environmental effect may be mediated via the effect of environmental microbiota on the commensal microbiota influencing immunotolerance.
Cites: Proc Natl Acad Sci U S A. 2010 Aug 17;107(33):14691-620679230
Cites: Proc Natl Acad Sci U S A. 2012 May 22;109(21):8334-922566627
To study the associations between timing and diversity of introduction of complementary foods during infancy and atopic sensitization in 5-year-old children.
In the Finnish DIPP (type 1 diabetes prediction and prevention) birth cohort (n = 3781), data on the timing of infant feeding were collected up to the age of 2 years and serum IgE antibodies toward four food and four inhalant allergens measured at the age of 5 years. Logistic regression was used for the analyses.
Median duration of exclusive and total breastfeeding was 1.4 (interquartile range: 0.2-3.5) and 7.0 (4.0-11.0) months, respectively. When all the foods were studied together and adjusted for confounders, short duration of breastfeeding decreased the risk of sensitization to birch allergen; introduction of oats
The objective of the present study was to assess the prevalence of asthma and asthma-related symptoms in Finland. We also wondered whether chronic cough may be an indicator of occult asthma. Prevalence and characteristics of children with doctor-diagnosed asthma and chronic respiratory symptoms were investigated in 7-12 year old school children from eastern Finland by using a questionnaire on respiratory symptoms. In addition, skin-prick tests, flow-volume spirometry, and serum total immunoglobulin E (IgE) measurements were performed in children reporting chronic respiratory symptoms. The parent-reported prevalence of doctor-diagnosed asthma was 4.4%, of wheezing 5.4%, of attacks of shortness of breath with wheezing 4.6%, and of dry cough at night 12%. Children with dry cough only (n = 195) had less frequent parental asthma, self-reported allergies, daily respiratory medication, and moisture stains or molds at home than asthmatic children (n = 180), but these findings were more frequent than among asymptomatic children (n = 2,169). The prevalence of at least one positive skin-prick test result was 79% among the asthmatic children and 55% among children with dry cough only. There were no differences between the two symptom groups in serum total IgE levels and spirometric lung functions, except in maximal mid-expiratory flow (MMEF) values, which were significantly lower among children with asthmatic symptoms. The present results support the hypothesis that chronic cough may be an indicator of occult asthma. Therefore, to improve the sensitivity of respiratory questionnaires designed to detect asthma, they should also include questions on chronic cough.(ABSTRACT TRUNCATED AT 250 WORDS)