What is it about?

Exposure to farming environments is one of the strongest and most replicated protective factors against asthma development. This article, published in 2012, systematically identified and summarizes the existing evidence up to end of 2011. Several additional studies have been published since then, some of them can be identified among the articles citing this systematic review.

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Why is it important?

Researchers and decision makers are faced with an ever increasing number of original research articles on a given topic, which can cloud the issue or be impossible to grasp in detail. Systematic reviews with meta-analysis have been a useful approach to synthesize original evidence for these users. This article helped reseachers to focus their subsequent studies on aspects of the so-called protective 'farm effect' that had been underresearched or less clear.


Some argue that meta-analyses of observational studies are meaningless due to residual confounding in observational studies. Certainly meta-analysis of observational studies does not have such a clear-cut interpretation as for randomized controlled trials. However, it still provide a synthesis of the existing evidence and can point the user to potential reasons for heterogeneity in risk estimates of original studies. Moreover, the mere listing of original articles on a given topic can improve notice and valuation of previous research and may help in reducing research waste.

PD Dr. med. Jon Genuneit
Universitat Leipzig

Read the Original

This page is a summary of: Exposure to farming environments in childhood and asthma and wheeze in rural populations: a systematic review with meta-analysis, Pediatric Allergy and Immunology, May 2012, Wiley, DOI: 10.1111/j.1399-3038.2012.01312.x.
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