The association between Helicobacter pylori infection and asthma risk: an updated systematic review and meta-analysis

BACKGROUND: Although Helicobacter pylori (H. pylori) has been hypothesized to modulate immune responses in the context of asthma, recent epidemiological evidence has yielded contradictory results. This updated meta-analysis systematically re-evaluates the association between H. pylori infection and asthma risk to clarify these discrepancies. METHODS: A systematic review and meta-analysis were conducted following PRISMA 2020 guidelines. We systematically searched PubMed, Web of Science, Cochrane Library, and Embase up to February 2026 to identify eligible observational studies. To evaluate the risk association, pooled odds ratios (ORs) and hazard ratios (HRs) with 95% confidence intervals (CIs) were calculated, utilizing either fixed- or random-effects models contingent upon the degree of statistical heterogeneity. RESULTS: 43 studies encompassing 240,715 individuals were included. Stratification by study design yielded diverging results: retrospective case-control studies indicated a significant inverse association (OR 0.78, 95% CI 0.63-0.95), whereas prospective cohort data suggested a positive association with asthma incidence (HR 1.13, 95% CI 1.07-1.19). Furthermore, subgroup analyses identified a robust inverse association in individuals infected with high-virulence CagA-positive strains (OR 0.75, 95% CI 0.62-0.90), which remained consistent across different study designs. In contrast, the inverse association observed in pediatric populations (OR 0.60, 95% CI 0.46-0.79) appeared sensitive to the underlying study design and diagnostic framework. CONCLUSION: In conclusion, the H. pylori-asthma association is highly dependent on study design and clinical context. While overall results remain uncertain due to diverging retrospective and prospective findings, we identified a robust inverse association in CagA-positive groups that is consistent across study designs. In contrast, findings in pediatric populations are sensitive to methodological variations, necessitating cautious interpretation. These results indicate H. pylori does not exert a uniform effect; rather, the relationship is likely moderated by pathogen virulence and host factors. Consequently, our findings warrant significant caution, and future prospective research is essential to determine their clinical relevance.