Helicobacter pylori (H. pylori) is a significant gastric pathogen, infecting over 50% of the global population. Numerous studies have linked H. pylori infection to both gastric and extra-gastric diseases. Given a considerable subject-between heterogeneity in the effects, it is crucial to assess the individual health effects of H. pylori, i.e., the effects in subjects with specific covariates. Distinguished from the previous studies that typically focused on a single covariate using a subgroup analysis and merely established the association without assessing the causal effect, this project aims to comprehensively assess the multi-covariate-specific causal effects of H. pylori infection on gastric and extra-gastric diseases by developing a novel approach which combines the flexible semi-parametric model (or nonparametric model) with the causal inference tools, such as mendelian randomization. The covariates will include sex, age, polygenic risk scores, health condition, natural environmental factors, smoking, drinking and other common lifestyle habits. This project could help identify which H. pylori-infected individuals are at a higher risk for specific diseases, ultimately improving the management and treatment of those infected.
