Is Helicobacter Pylori infection inversely associated with atopy? A systematic review and meta-analysis

Background: The role Helicobacter Pylori (H. pylori) infection plays in the etiology of atopy remains unclear, although a possible protective role has been hypothesized. Objective: The aim of this study was to undertake a systematic review and meta-analysis of epidemiological studies to quantify the association between H. pylori infection and atopy. Methods:
A comprehensive literature search in MEDLINE/PUBMED and EMBASE (up to August 2013) was carried out to identify all observational epidemiological studies (cross-sectional, cohort, case–control) published in English that evaluated the association between H. pylori infection and objectively measured atopy (measured by allergen skin tests or specific IgE). The quality of included studies was assessed by the Newcastle-Ottawa scale. Random-effects meta-analyses were performed to obtain pooled estimates of effect. Results: Twenty-two observational studies involving 21,348 participants were identified as eligible for inclusion in the review, of which 16 were included in the meta-analysis. H. pylori infection was associated with a significantly reduced odds of atopy (pooled odds ratio (OR) 0.82; 95% confidence interval (CI) 0.73–0.91; P < 0.01). Subgroup analysis according to atopy definition revealed a slightly greater protective effect for atopy defined as raised allergen specific IgE (OR 0.75; 95% CI 0.62-0.92; P < 0.01; 7 studies). Findings did not differ according to the population age (adult or children), methodological quality or study design. Conclusion and Clinical Relevance: Evidence from epidemiological studies suggests that
H. pylori infection is associated with an estimated 18% reduction in odds of atopy. If the observed association is causal, more insights into the underlying mechanisms could provide clues to possible therapeutic opportunities in allergic disease.