Farm living and risk of asthma, atopic eczema, respiratory and food allergy: protocol for a systematic review and meta-analysis

INTRODUCTION: Asthma and allergic disorders are of global concern and risk for their development results from the interplay of genetic and environmental factors. Among numerous environmental factors identified to influence the disease risk, the role of exposure to a farming environment has gained interest in recent times, but the underlying evidence is conflicting. The review aims to comprehensively identify, critically appraise and synthesise evidence from studies investigating the association between farm living and risk of asthma and allergic diseases in children and adults. METHODS AND ANALYSIS: We will identify relevant analytical observational epidemiological studies, including cross-sectional, case-control and cohort studies, by searching PubMed, Cochrane Library, Google Scholar, Cumulative Index to Nursing and Allied Health Literature (CINAHL), WHO Global Health Library, Web of Science, Scopus and Embase. Screening of identified records, data extraction from eligible studies and risk of bias assssment of eligible studies will be independently undertaken by two reviewers, with arbitration by a third reviewer. The Effective Public Health Practice Project will be employed for the risk of bias assessment. Estimates from studies judged to be clinically, methodologically and statistically homogeneous will be synthesised using random-effects meta-analysis. Heterogeneity will be assessed using the I-squared statistic. We will consider objectively measured or self-reported asthma, atopic dermatitis/eczema, allergic rhinitis, wheeze, and food allergy as primary outcomes. ETHICS AND DISSEMINATION: As this study is based solely on the published literature, no ethics approval is required. The study findings will be presented at scientific meetings related to the field of asthma and allergy and will be published in an international peer-reviewed scientific journal. PROSPERO REGISTRATION NUMBER: CRD42020208805.