Environmental and occupational respiratory disorders
Not all farming environments protect against the development of asthma and wheeze in children

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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.

Clinical implications

The development of atopic sensitization and atopic and nonatopic asthma is most likely determined by different environmental factors, possibly reflecting distinct pathomechanisms.

Section snippets

Population and study areas

The PARSIFAL study was a cross-sectional survey on children of farmers, children attending Rudolf Steiner schools, and their respective reference groups. The study was carried out as described previously.21 In the farming branch of the study, children aged 5 to 13 years from rural areas of Austria, Germany, The Netherlands, Sweden, and Switzerland were invited to participate. Of the 11,969 invited children, 8402 (70%) returned the questionnaires. A total of 139 children were excluded because of

Characteristics of farms and children's activities on farms

Information on farms is provided in Table I. The questions regarding farm characteristics were not mutually exclusive, and therefore percentages do not sum up to 100%. Because the PARSIFAL study was deliberately performed in regions of dairy farming, the predominant form of farming was livestock, in particular cattle. Yet substantial numbers of other animals were kept on the farms as well. Of the livestock farms, 37% also performed agriculture, most likely to provide fodder for their animals.

Discussion

The present study revealed distinct protective exposures for asthma and wheeze (agriculture, pig farming, silage, haying, farm milk, animal sheds, and barns). Most of these exposures were related to the atopic phenotypes, but silage exerted a protective effect only on the nonatopic phenotype. Furthermore, potential risk factors for asthma and wheeze have been identified in the farm milieu (sheep and hare keeping and using hay as feed). For atopic sensitization, agriculture, pig, and poultry

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  • Cited by (0)

    Supported by a research grant from the European Union (QLRT 1999-01391) and by funding from the Swedish Foundation for Health Care Science and Allergy Research, the Swiss National Foundation (grant no. 32-100324), the Kühne-Foundation, and the European Union Framework program for research (contract no. FOOD-CT-2004-506378, the Global Allergy and Asthma European Network [GA2LEN]).

    Disclosure of potential conflict of interest: The authors have declared that they have no conflict of interest.

    The Prevention of Allergy Risk Factors for Sensitization in Children Related to Farming and Anthroposophic Lifestyle (PARSIFAL) study group: Tobias Alfvén, Johan Alm, Anna Bergström, Lars Engstrand, Helen Flöistrup, Niclas Håkansson, Gunnar Lilja, Jackie Swartz, Magnus Wickman, Annika Scheynius (Sweden); Roger Lauener, Felix Sennhauser, Johannes Wildhaber, Alex Möller (Switzerland); Gert Doukes, Mirian Boeve, Jeroen Douwes, Machteld Huber, Mirjam Matze (The Netherlands); Jörg Budde (Germany); Waltraud Eder, Mynda Schreuer, Ellen Üblagger (Austria); Karin B. Michels (USA).

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