Probiotics: A Possible Preventative Measure of Atopic Asthma?

Abstract

Introduction: Asthma is a chronic inflammatory immune disorder characterized by acute episodes of bronchial hyper responsiveness. This is caused by recurrent dysregulation of several immunoregulatory proteins such as interleukins, cytokines, clusters of differentiation, and immunoglobulins . In Canada and the U.S, the risks of developing atopic asthma can range from 1 case in every 10 children (general population), to 1 case in every 5 children (high-risk populations: African American descent). Asthma has an incidence rate of 8.5 million cases each year while the prevalence is 161.3 cases /1000 person years, depending on the population and environment studied. Children with decreased microbial exposure were observed to develop an altered gut microbiota leading to a higher risk for the development of asthma and allergic diseases. Objective: The aim of this review is to examine if probiotics decrease the risk of developing atopic asthma in children with an abnormal gut microbiome. Methodology: Concepts pertaining to the research question were identified and expanded upon through keywords: risk, and asthma or immune function, and probiotics or gut microbiome. Peer reviewed journals published between the years 2007-2017, from Canada and/or U.S.A were examined. Exclusion criteria included terms relating to airway, throat and respiratory microbiota to eliminate articles irrelevant to the focus of this study. The search strategy was developed on PubMed and adapted to Scopus, Journal of Allergy and Clinical Immunology and Journal of Pediatric Allergy and Immunology to yield the most relevant research articles. This resulted in 61 articles, from which 8 relevant articles were deemed eligible for the making of this literature review. Results: The 8 most relevant studies consisted of 2 systematic reviews and meta-analyses (one being meta-analysis only), 2 prospective nested case-control studies, and only 1 cohort and RCT each. The RCT study showed a positive correlation between the administration of probiotics and the reduction of asthma onset, while all three case-controls and cohorts listed an altered gut microbiota as a causative risk factor for developing asthma. Lastly, the 2 systematic reviews and meta-analyses concluded that no clinically-relevant association was present between the administration of probiotics and the prevention of asthma development. Conclusion: Due to the large heterogeneity of results, little compiled evidence supports a relation between the delivery of probiotics and the prevention of asthma development as of yet. Studies more specific to probiotics in relation to asthma development in larger cohorts need to be conducted to better understand any possible associations.