Associations of Helicobacter Pylori with Anemia: A Bidirectional Two-Sample Mendelian Randomization Study

Associations of Helicobacter Pylori with Anemia: A Bidirectional Two-Sample Mendelian Randomization Study | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Associations of Helicobacter Pylori with Anemia: A Bidirectional Two-Sample Mendelian Randomization Study Chuqi Xia, Wanyang Lei, Yongyu Yang, Guowu Sun, Yang Zhang, Xinyue Li, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-3940357/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Background Observational studies have reported a correlation between Helicobacter pylori infection and an increased incidence of anemia, iron deficiency anemia (IDA), and vitamin B12 deficiency anemia. However, the fundamental cause remains elusive. This study aimed to ascertain the causal relationship between H. pylori infection and anemia. Method Using data from genome-wide association studies (GWAS), we executed a bidirectional Mendelian randomization (MR) study utilizing two-sample GWAS. The principal analytical method was the inverse variance weighted (IVW) method. We employed a conservative Bonferroni-corrected threshold (p < 2.38 × 10 − 3 ). Sensitivity analyses were implemented with Cochran’s Q test and MR-Egger regression. Results Genetically predicted H. pylori infection, anti- H. pylori CagA, VacA, and IgG seropositivity was not causally associated with anemia, IDA, or vitamin B12 deficiency anemia (p > 2.38 × 10 − 3 ). Furthermore, reverse MR analysis did not reveal evidence for a causal effect of anemia on H. pylori infection (p > 0.05). Conclusions Utilizing genetic data, MR analysis demonstrated the absence of evidence for a causal association between the seroprevalence of H. pylori infection and anemia. Further research is needed to elucidate the relationship between H. pylori infection and anemia. Helicobacter pylori anemia iron deficiency anemia vitamin B12 deficiency anemia Mendelian Randomization Figures Figure 1 Figure 2 1. Introduction Helicobacter pylori , a gram-negative, microaerophilic bacterium predominantly inhabiting the gastric epithelium, has been unequivocally implicated in a plethora of gastroduodenal pathologies, most notably peptic ulcer disease and gastric adenocarcinoma 1, 2 . The organism's role in these conditions has been well-characterized, and bolstered by decades of rigorous scientific inquiry. However, recent studies have expanded the understanding of the influence of H. pylori , highlighting its association with diseases beyond the gastroduodenal system, including iron deficiency anemia (IDA), immune thrombocytopenic purpura, vitamin B12 deficiency, metabolic syndrome, diabetes mellitus and so on 3 . Various pathogenic mechanisms, including the occurrence of molecular mimicry and the induction of low-grade inflammation, have been hypothesized 4 . It is well known that H. pylori infection can induce chronic gastritis, resulting in gastric mucosa damage, which may affect the absorption of nutrients such as vitamin B12 and iron 5 . Therefore, significant research interest has been directed toward the association between H. pylori infections and nutritional anemia. To our knowledge, a growing body of observational studies has reported an association between H. pylori infection and the higher prevalence of anemia, iron deficiency, IDA, vitamin B12 deficiency, and vitamin B12 deficiency anemia 6, 7 . A meta-analysis of 15 case-control studies revealed a substantial increase in IDA risk among H. pylori -infected patients, with an odds ratio (OR) of 2.2 (95% CI:1.5–3.2) 8 . This link is believed to originate from H. pylori- induced chronic gastritis, leading to gastric mucosal damage and occult blood loss, resulting in iron deficiency and IDA 9 . Additionally, Sarari et al. reported vitamin B12 deficiency in 67.4% of H. pylori -infected patients 10 , likely due to gastritis-induced atrophic changes in the gastric mucosa, impairing vitamin B12 absorption 11 . These associations, while supported by epidemiological data, remain speculative due to observational studies' limitations, such as confounding variables and inability to establish causality. In this regard, Mendelian randomization (MR) has emerged as a valuable tool for exploring the causal effects of H. pylori infection on anemia. Using genetic variants (single nucleotide polymorphisms, SNPs) as instrumental variables (IVs), MR circumvents the typical confounders of observational research and overcomes reverse causation bias 12 . Studies using MR have offered new insights into the impact of H. pylori on various diseases. For instance, Chen et al. 13 identified a link between H. pylori IgG antibodies and an increased risk of gastroesophageal reflux disease, while Liu et al. 14 found no genetic evidence for a causal relationship between H. pylori and nonalcoholic fatty liver disease. These findings highlight the potential of MR to inform prevention and treatment strategies for H. pylori infection. Therefore, we employed a bidirectional two-sample MR approach to delve deeper into the causal relationship between H. pylori infection and anemia. Considering the findings from previous observational studies and the limitations of available database resources, the data for SNPs associated with anemia, IDA, and vitamin B12 deficiency anemia from the latest release of the FinnGen Biobank (R10, December 2023) were chosen in our research. Meanwhile, SNPs associated with susceptibility to H. pylori infection were identified through literature search or genome-wide association studies (GWAS) summary data analysis, involving data on H. pylori seropositivity, anti- H. pylori CagA, VacA, and IgG levels. Our goal is to elucidate potential genetic mechanisms linking H. pylori infection to anemia, IDA, and vitamin B12 deficiency anemia, providing a foundation for disease prevention strategies. 2. Materials and Methods 2.1. Study Design and Framework This investigation employs a two-sample bidirectional MR framework, utilizing SNPs as IVs to explore the causal effects of H. pylori infection on anemia, IDA, and vitamin B12 deficiency anemia. Three assumptions must be met to confirm the validity of MR analysis: (1) genetic variants directly affect the risk factor; (2) genetic variants are not associated with any known or unknown confounders; and (3) genetic variants affect the outcome through only the risk factor and not through other pathways. For a detailed discussion of these assumptions, refer to Greenland 15 . Figure 1 presents a schematic diagram summarizing the MR assumptions and a flowchart illustrating our bidirectional two-sample MR analysis. The datasets used in this study are available from public databases and received ethical approval before implementation. This study, therefore, did not require additional ethical approval. 2.2. Data Source and Study Population SNPs associated with susceptibility to H. pylori infection were identified via either a literature search or a GWAS summary data analysis. The data for SNPs associated with H. pylori infection were composed of H. pylori seropositivity, anti-H. pylori CagA, anti- H. pylori VacA, and anti- H. pylori IgG. SNPs associated with H. pylori infection were identified in a study conducted by Mayerle et al. 16 on a European population that included 2763 cases and 8175 controls. SNPs associated with anti- H. pylori CagA from the European Bioinformatics Institute (EBI) database included 985 samples with 9,165,056 SNPs 17 . SNPs associated with anti- H. pylori VacA from the GWAS meta-analysis of EBI data included 1,571 samples with 9,178,635 SNPs 17 . Similarly, SNPs associated with H. pylori IgG seropositivity according to the GWAS meta-analysis of EBI data included 4,683 samples with 7,247,045 SNPs. Further information about OpenGWAS can be found at https://gwas.mrcieu.ac.uk/ . To prevent participant overlap, genomic data on anemia traits were obtained from the FinnGen Biobank (R10). In the FinnGen consortium, anemia included 30,092 cases and 94,450 controls of European ancestry, IDA included 15,153 cases and 393,684 controls of European ancestry, vitamin B12 deficiency anemia included 3,694 cases and 393,684 controls of European ancestry 18 . All participants were of European ancestry. All the original studies obtained ethical approval and informed consent. The details of the included GWASs are summarized in Table 1 . Table 1 Details of the studies in the mendelian randomization analysis. HP: Helico-bacter pylori, EBI: European Bioinformatics Institute, IDA: iron deficiency anemia, VB12DA: vitamin B12 deficiency anemia. Exposure or outcome Consortium or author Population Sample size Year Web source HP infection Mayerle et al. European 10,938 2013 https://jamanetwork.com/journals/jama/fullarticle/1685857 Anti-HP CagA EBI European 985 2020 https://gwas.mrcieu.ac.uk/datasets/ebi-a-GCST90006911/ Anti-HP VacA EBI European 1,571 2020 https://gwas.mrcieu.ac.uk/datasets/ebi-a-GCST90006916/ Anti-HP IgG EBI European 4,683 2021 https://gwas.mrcieu.ac.uk/datasets/ieu-b-4905/ Anemia Finngen (R10) European 124,542 2023 https://storage.googleapis.com/finngen-public-data-r10/summary_stats/finngen_R10_D3_ANAEMIA.gz IDA Finngen (R10) European 408,837 2023 https://storage.googleapis.com/finngen-public-data-r10/summary_stats/finngen_R10_D3_ANAEMIA_IRONDEF.gz VB 12 DA Finngen (R10) European 397,378 2023 https://storage.googleapis.com/finngen-public-data-r10/summary_stats/finngen_R10_D3_ANAEMIA_B12_DEF.gz 2.3. Instrumental Variable Selection and Validation We conducted a series of stringent quality control measures to select IVs that adhere to the three fundamental assumptions of MR analysis, thereby ensuring its robustness and reliability. Initially, genetic variants linked to the exposure were pinpointed at the genome-wide significance level ( p < 5 × 10 − 8 ). If an adequate number of IVs are not found at this threshold, a more relaxed threshold ( p < 5 × 10 − 6 ) will be adopted. Two SNPs, rs10004195 and rs368433, identified in Mayerle et al.'s 16 study as independently and strongly linked to H. pylori seropositivity, were classified as IVs. Secondly, any SNP significantly associated with the outcome was excluded. Thirdly, SNPs were clumped with a threshold of r 2 = 0.001 and a window size of 10mb assessed in the European 1,000 genomes reference panel. Fourth, SNPs potentially demonstrating pleiotropic effects were eliminated. Specifically, we utilized the MR Pleiotropy Residual Sum and Outlier (MR-PRESSO) method to assess outliers for pleiotropy. Fifth, we calculated the F statistic \((\varvec{F}={\varvec{b}\varvec{e}\varvec{t}\varvec{a}}^{2}/{\varvec{s}\varvec{e}}^{2})\) to address potential bias from weak IVs; an F statistic less than 10 suggested an invalid IV. Ambiguous and palindromic SNPs were harmonized to ensure accuracy. 2.4. Statistical analyses We utilized a bidirectional two-sample MR approach to investigate the causal relationship. The foundation of our study was inverse variance weighted (IVW) analysis, which acted as the principal method of analysis. In the presence of potential heterogeneity among the analyzed SNPs, our analysis employed a random-effects inverse-variance model. We also adopted complementary methods, such as MR-Egger and weighted median analyses. Notably, to tackle the issue of multiple testing, we adopted a conservative Bonferroni-corrected threshold ( p < 2.38 × 10 − 3 ), because 21 causalities were evaluated for this bidirectional analysis. The MR analysis was performed using the R software environment (version 4.3.1), utilizing the TwoSampleMR (version 0.5.7) and MRPRESSO (version 1.0) packages. 2.5. Sensitivity analyses A multistep process was conducted for sensitivity analysis and to assess the second and third assumptions. Initially, Cochran’s Q test was used to evaluate heterogeneity among the IVs. Subsequently, the MR-Egger regression was employed to assess the potential horizontal pleiotropy of the IVs. 3. Results 3.1 Instrumental Variables To analyze the effects of H. pylori infection on anemia, IDA, and vitamin B12 deficiency anemia. Firstly, two SNPs (rs10004195 and rs368433) from the study by Mayerle et al. 16 were identified as independent and strongly associated with H. pylori seropositivity, and were regarded as IVs. The F-statistics for these IVs were 81 and 26.69, respectively, effectively avoiding the impact of weak IVs on the causal effect. We subsequently selected 15 SNPs for H. pylori CagA antibody levels, 15 SNPs for H. pylori VacA antibody levels, and 12 SNPs for anti-H. pylori IgG levels as IVs with a genome-wide significance of p < 5 × 10 − 6 . To analyze the effects of anemia, IDA, and vitamin B12 deficiency anemia on H. pylori infection, we selected at least 2 and up to 13 SNPs for anemia, IDA, and vitamin B12 deficiency anemia as IVs with a genome-wide significance of p < 5 × 10 − 8 . Several analyses were unsuccessful due to the absence of SNPs post-harmonization. The F-statistic for IVs suggested that the estimates were unlikely to suffer from weak instrumental bias (F > 10). The detailed information of IVs of exposures is presented in Supplementary Table S2 . 3.2 Causal effect of H. pylori infection on Anemia, Iron Deficiency Anemia, and Vitamin B12 deficiency anemia The results of MR estimates using IVW are presented in Fig. 2 . And other different several philosophies are presented in Supplementary Table S2 . There was no evidence of a causal connection between having a genetic predisposition to H. pylori infection and an increased risk of anemia, IDA, or vitamin B12 deficiency anemia. The primary IVW method showed that genetically predicted H. pylori seropositivity in Mayerle et al.’s 16 study was not causally associated with anemia [OR = 0.97, 95% confidence interval (CI): 0.91–1.05, p = 0.49], with IDA (OR = 0.96, 95% CI: 0.89–1.03, p = 0.24), or with vitamin B12 deficiency anemia (OR = 0.88, 95% CI: 0.72–1.08, p = 0.22) in FinnGen Biobank (R10). In addition, the MR estimates showed that the causal effect of anti-H. pylori CagA, VacA, and IgG levels on anemia and its subtypes was the same as that of H. pylori infection on anemia (p > 2.38 × 10 − 3 , Bonferroni-corrected threshold). The direction is consistent across sensitivity analyses, including MR-Egger and weighted median. Notably, the results of genetic causal effect of anti- H. pylori CagA (OR = 0.93, 95% CI: 0.87-1.00, p = 0.04) and anti- H. pylori IgG (OR = 0.90, 95% CI: 0.83–0.98, p = 0.01) on an increased risk of IDA ranged 2.38 × 10 − 3 and 0.05, which implies that there may be a potential causal effect of anti-H. pylori CagA and IgG levels on a reduced risk of IDA. 3.3 Causal effect of Anemia, Iron Deficiency Anemia, and Vitamin B12 Deficiency Anemia on H. pylori infection The IVW results showed that genetically predicted anemia and its subtypes had no genetic causal relationship with H. pylori infection ( p > 0.05) (Fig. 2 , Supplementary Table S1 ). Anemia was not causally associated with anti- H. pylori CagA (OR = 1.01, 95% CI: 0.67–1.54, p = 0.95), with anti-H. pylori VacA (OR = 0.89, 95% CI: 0.69–1.15, p = 0.37), or with anti- H. pylori IgG (OR = 1.38, 95% CI: 1.00-1.90, p = 0.05); IDA was not causally associated with anti- H. pylori CagA (OR = 0.92, 95% CI: 0.65–1.31, p = 0.64), with anti- H. pylori VacA (OR = 1.04, 95% CI: 0.78–1.40, p = 0.79), or with anti- H. pylori IgG (OR = 1.09, 95% CI: 0.89–1.32, p = 0.41); vitamin B12 deficiency anemia was also not causally associated with anti- H. pylori CagA (OR = 0.88, 95% CI: 0.74–1.04, p = 0.12), with anti- H. pylori VacA (OR = 0.94, 95% CI: 0.84–1.05, p = 0.29), or with anti- H. pylori IgG (OR = 1.04, 95% CI: 0.92–1.18, p = 0.54). The sensitivity analyses of both weighted median approach and the MR-Egger method generated identical results. 3.4 Sensitivity analyses All P values from the Cochran Q tests exceeded 0.05, signifying a lack of observable heterogeneity. Insufficient evidence was found for horizontal pleiotropy, as all P values from subsequent Egger intercept exceeded 0.05. Sensitivity analysis results are presented in Supplementary Table S2 . 4. Discussion In this study, we refrained from directly comparing H. pylori serology with anemia, IDA and vitamin B12 deficiency anemia. Instead, we adopted a bidirectional MR approach by using potential SNPs associated with H. pylori infection from four genetic data pools as IVs. To provide additional context, we referenced prior research, including the study by Mayerle et al. 16 . Meanwhile, SNPs associated with anemia were identified from three genetic data pools from the latest release of the FinnGen Biobank (R10, December 2023). This approach aimed to evaluate the potential causal relationship between H. pylori and anemia. Our results suggest that there is no causal effect of genetic predisposition to H. pylori infection on the risk of anemia, IDA, and vitamin B12 deficiency anemia. This consistency in results persisted across various MR sensitivity analysis methods. While acknowledging that factors such as hygiene standards and family history influence H. pylori infection, we also recognize the need for further replication and validation of the identified SNPs as surrogate biomarkers for predicting H. pylori infection. Nonetheless, our primary objective was to delve into the potential genetic factors associated with this relationship, thereby enhancing our understanding of the biology of H. pylori -related nutrition-related diseases. This section provides an in-depth analysis, situating our findings within the existing body of research. To our knowledge, there is no inconsistent evidence on the association of H. pylori infection with an increased risk of anemia, IDA, and vitamin B12 deficiency. A large cross-sectional study conducted by Eyoum Bille et al. 19 in 2022 revealed that compared with H. pylori non-infected participants, H. pylori infected patients were 1.2938 (95%CI: 0.9087–1.8421), 1.1851 (95%CI: 0.8122–1.7292), and 1.5636 (95%CI: 1.0206–2.3953) times at higher risk to develop anemia, iron deficiency, and IDA, respectively, and a significant relationship was found between H. pylori infection and IDA ( p = 0.04). A lastest meta-analysis of 14 observational studies by Hudak et al. 20 reported similar conclusion: compared to uninfected persons, H. pylori -infected individuals showed an increased likelihood of IDA. A well-recognized explanation for this phenomenon is that H. pylori chronic gastritis can change the physiology of the stomach, inducing reductions in gastric acid secretion and gastric ascorbic acid levels, which are essential for the absorption of dietary iron 20 . Many studies have also shown a relationship between H. pylori infection and vitamin B12 deficiency. In 2019, Ulasoglu et al. 21 found that cytotoxin-associated gene-A (CagA) seropositivity, which is one of the virulence factors of H. pylori , was positively correlated with B12 deficiency. In 2020, a descriptive cross-sectional study conducted by Gökışık et al. 22 , which included 421 patients, reached a similar conclusion: the rate of vitamin B12 deficiency was significantly higher among patients with H. pylori infection. This may be due to the fact that a result of H. pylori -induced gastritis and ulcers is destruction of the parietal cells which are important for the production of intrinsic factor which is essential for vitamin B12 absorption 10 . Nevertheless, a little scholarship supported that the absence of a correlation between H. pylori infection and anemia. In 2022, Lee et al. 23 identified 1,069 non-elderly adults participating in a health check-up program, and found that there was no significant difference in anemia or IDA with H. pylori In 2019, Mendoza et al. 24 performed a cross-sectional study on school-age children, and found that the association between H. pylori and iron deficiency was not significant for lower values of hepcidin (OR = 0.17; 95% CI: 0.02–1.44). In 2023, Pinar et al. 25 also found that there was no relationship between the presence or density of H. pylori with vitamin B12 levels. Meanwhile, most studies primarily assess H. pylori status and measure serum vitamin B12 levels, yet there are no sufficient interventional studies demonstrating the impact of anti- H. pylori therapy on vitamin B12 deficiency 3 . There are a number of possible explanations for the controversy surrounding H. pylori infection and the risk of nutrition-related diseases. First, there were no prospective, randomized, or blinded methods in any of these epidemiologic observational studies. Potential confounding factors might exist, including environmental and genetic factors. These confounders might simultaneously affect the onset and progression of H. pylori infection, IDA and vitamin B12. Second, different studies have used different diagnostic strategies for H. pylori infections and nutrition-related diseases. Based on the global guidelines of the World Gastroenterology Organization (WGO) 26 , the urine breath test is the most recommended non-invasive test to check for H. pylori infection. However, some studies measured H. pylori infection using serum or IgG antibodies to H. pylori or H. pylori DNA sequences, and therefore, the criteria for the diagnosis of H. pylori infection were inconsistent across studies 21, 24, 27 . Similarly, even though the World Health Organization (WHO) has established criteria for the diagnosis of malnutrition, there may be differences in diagnostic criteria and testing techniques across countries and regions 28 . Third, these differences could be attributed to differences in age, sex, geographic region, ethnicity, dietary habits, socioeconomic status, anti- H. pylori IgG titers, and anti- H. pylori antibody types and levels. Our research is the first attempt to clarify the connection between H. pylori infection and anemia from the perspective of genetic variation. Based on the thorough assumptions underpinning the relationship between genetic predisposition and outcome, in line with the principles of bidirectional MR, we found no convincing evidence to suggest a causal link between H. pylori infection and the risk of anemia, IDA, or vitamin B12 deficiency anemia. Although randomized controlled trials are widely considered the most reliable approach for dentifying the presence of a causal relationship, it is not always possible to carry one out due to its high cost. However, since SNPs are randomly allocated at conception, MR studies can successfully correct for this potential confounding bias. Unlike the approaches used in other observational studies, MR offers the advantage of being able to address the reverse causality problem. Second, our study results may have implications for healthcare policies regarding H. pylori infection and anemia. Given the high incidence of H. pylori infection in the general population, establishing causation between H. pylori infection and anemia can affect public health strategies for early prevention and appropriate intervention 29 . Our results indicate that anti- H. pylori therapy may not be beneficial in the treatment of anemia, IDA, or vitamin B12 deficiency anemia. Consequently, this might contribute to significant reductions in public healthcare costs and the conservation of healthcare resources. However, there are several limitations in our study. First, potential confounding factors and reverse causality might exist, and the diagnosis of H. pylori infection was based on serological testing in the GWAS data, which may have biased on the detection of H. pylori infection. And we can not ascertain the relative time of H. pylori infection and anemia development when they collected the clinical samples, some pathophysiologic changes in anemia might exist and lead to H. pylori infection before clinical diagnosis of anemia. Second, in our MR analysis, only two SNPs were signifcantly and independently linked to H. pylori infection, while the remaining SNPs were associated with anti-HP CagA, Vac A, and IgG. These SNPs may not be perfect IVs and may lead to errors in the results. Third, MR is based on genetic variants, which reflects the long-term impact of H. pylor i infection on anemia susceptibility across a lifetime. H. pylor i infection is influenced by factors like hygiene standards and family history. Anemia, IDA, and vitamin B12 deficiency anemia is influenced by factors like dietary habit and nutrient intake. And the influence of H. pylor i infection on anemia may vary significantly in the short term. Fourth, the databases employed were limited to European populations, constraining their generalizability to other racial groups. In summary, while we acknowledge the limitations and complexities of studying the association between H. pylori and anemia, we believe that our study provides valuable insights by employing Mendelian randomization. 5. Conclusions In summary, this MR study contributes to the ongoing discourse on the systemic effects of H. pylori infection by providing evidence against a direct genetic causal relationship with anemia, IDA, and vitamin B12 deficiency. This underscores the complexity of these conditions and the importance of using genetically informed methods to discern true causal relationships in epidemiological research. Declarations Author contributions: D.L. and N.X. designed the study. C.X. and W.L. analyzed the datasets and interpreted the results. G.S. and Y.Y. downloaded the data. Y.Z and X.L. provided software support. C.X. and W.L. wrote and edited the manuscript. D.L. provided the foundation and support. All the authors have read and agreed to the published version of the manuscript. Financial: This study is funded by National Natural Science Foundation of China (8236030102) and Joint Special Fund of Applied Fundamental Research of Kunming Medical University granted by Science and Technology Office of Yunnan (202301AY070001-025). Institutional Review Board Statement: Not applicable. Informed Consent Statement: The data originated from a publicly accessible database, and as no human participants were involved, ethical parameters were deemed inapplicable. Data Availability Statement: GWAS summary data of anemia, IDA, vitamin B12 deficiency anemia, anti- H. pylori CagA, anti- H. pylori VacA, and anti- H. pylori IgG, were downloaded from FinnGen (R10) and IEU consortium. For H. pylori seropositivity, the GWAS summary data were selected from associated GWAS studies. Potential competing interests: None. Ethics statement Ethical approval was not required for the study involving humans in accordance with the local legislation and institutional requirements. Written informed consent to participate in this study was not required from the participants or the participants’ legal guardians/next of kin in accordance with the national legislation and the institutional requirements. References Hathroubi, S.; Servetas, S. L.; Windham, I.; Merrell, D. S.; Ottemann, K. M., Helicobacter pylori Biofilm Formation and Its Potential Role in Pathogenesis. Microbiology and Molecular Biology Reviews : MMBR 2018, 82 (2). Morey, P.; Pfannkuch, L.; Pang, E.; Boccellato, F.; Sigal, M.; Imai-Matsushima, A.; Dyer, V.; Koch, M.; Mollenkopf, H.-J.; Schlaermann, P.; Meyer, T. F., Helicobacter pylori Depletes Cholesterol in Gastric Glands to Prevent Interferon Gamma Signaling and Escape the Inflammatory Response. Gastroenterology 2018, 154 (5). Tsay, F.-W.; Hsu, P.-I., H. pylori infection and extra-gastroduodenal diseases. Journal of Biomedical Science 2018, 25 (1), 65. Tshibangu-Kabamba, E.; Yamaoka, Y., Helicobacter pylori infection and antibiotic resistance - from biology to clinical implications. Nature Reviews. Gastroenterology & Hepatology 2021, 18 (9), 613-629. Wang, F.; Meng, W.; Wang, B.; Qiao, L., Helicobacter pylori-induced gastric inflammation and gastric cancer. Cancer Letters 2014, 345 (2), 196-202. Yuan, W.; Li, Y.; Yang, K.; Ma, B.; Guan, Q.; Wang, D.; Yang, L., Iron deficiency anemia in Helicobacter pylori infection: meta-analysis of randomized controlled trials. Scandinavian Journal of Gastroenterology 2010, 45 (6), 665-676. Shah, S. C.; Piazuelo, M. B.; Kuipers, E. J.; Li, D., AGA Clinical Practice Update on the Diagnosis and Management of Atrophic Gastritis: Expert Review. Gastroenterology 2021, 161 (4). Qu, X.-H.; Huang, X.-L.; Xiong, P.; Zhu, C.-Y.; Huang, Y.-L.; Lu, L.-G.; Sun, X.; Rong, L.; Zhong, L.; Sun, D.-Y.; Lin, H.; Cai, M.-C.; Chen, Z.-W.; Hu, B.; Wu, L.-M.; Jiang, Y.-B.; Yan, W.-L., Does Helicobacter pylori infection play a role in iron deficiency anemia? A meta-analysis. World Journal of Gastroenterology 2010, 16 (7), 886-896. Tan, H.-J.; Goh, K.-L., Extragastrointestinal manifestations of Helicobacter pylori infection: facts or myth? A critical review. Journal of Digestive Diseases 2012, 13 (7), 342-349. Sarari, A. S.; Farraj, M. A.; Hamoudi, W.; Essawi, T. A., Helicobacter pylori, a causative agent of vitamin B12 deficiency. Journal of Infection In Developing Countries 2008, 2 (5), 346-349. He, J.; Liu, Y.; Ouyang, Q.; Li, R.; Li, J.; Chen, W.; Hu, W.; He, L.; Bao, Q.; Li, P.; Hu, C., Helicobacter pylori and unignorable extragastric diseases: Mechanism and implications. Frontiers In Microbiology 2022, 13 , 972777. Skrivankova, V. W.; Richmond, R. C.; Woolf, B. A. R.; Davies, N. M.; Swanson, S. A.; VanderWeele, T. J.; Timpson, N. J.; Higgins, J. P. T.; Dimou, N.; Langenberg, C.; Loder, E. W.; Golub, R. M.; Egger, M.; Davey Smith, G.; Richards, J. B., Strengthening the reporting of observational studies in epidemiology using mendelian randomisation (STROBE-MR): explanation and elaboration. BMJ (Clinical Research ed.) 2021, 375 , n2233. Chen, J.; Zhang, J.; Ma, X.; Ren, Y.; Tang, Y.; Zhang, Z.; Ye, W.; Zhang, X.; Lin, Z.; Wang, L.; Li, Z., Causal relationship between Helicobacter pylori antibodies and gastroesophageal reflux disease (GERD): A mendelian study. PloS One 2023, 18 (12), e0294771. Liu, Y.; Xu, H.; Zhao, Z.; Dong, Y.; Wang, X.; Niu, J., No evidence for a causal link between Helicobacter pylori infection and nonalcoholic fatty liver disease: A bidirectional Mendelian randomization study. Frontiers In Microbiology 2022, 13 , 1018322. Greenland, S., An introduction to instrumental variables for epidemiologists. Int J Epidemiol 2000, 29 (4), 722-9. Mayerle, J.; den Hoed, C. M.; Schurmann, C.; Stolk, L.; Homuth, G.; Peters, M. J.; Capelle, L. G.; Zimmermann, K.; Rivadeneira, F.; Gruska, S.; Völzke, H.; de Vries, A. C.; Völker, U.; Teumer, A.; van Meurs, J. B.; Steinmetz, I.; Nauck, M.; Ernst, F.; Weiss, F. U.; Hofman, A.; Zenker, M.; Kroemer, H. K.; Prokisch, H.; Uitterlinden, A. G.; Lerch, M. M.; Kuipers, E. J., Identification of genetic loci associated with Helicobacter pylori serologic status. Jama 2013, 309 (18), 1912-20. Butler-Laporte, G.; Kreuzer, D.; Nakanishi, T.; Harroud, A.; Forgetta, V.; Richards, J. B., Genetic Determinants of Antibody-Mediated Immune Responses to Infectious Diseases Agents: A Genome-Wide and HLA Association Study. Open Forum Infectious Diseases 2020, 7 (11), ofaa450. Kurki, M. I.; Karjalainen, J.; Palta, P.; Sipilä, T. P.; Kristiansson, K.; Donner, K. M.; Reeve, M. P.; Laivuori, H.; Aavikko, M.; Kaunisto, M. A.; Loukola, A.; Lahtela, E.; Mattsson, H.; Laiho, P.; Della Briotta Parolo, P.; Lehisto, A. A.; Kanai, M.; Mars, N.; Rämö, J.; Kiiskinen, T.; Heyne, H. O.; Veerapen, K.; Rüeger, S.; Lemmelä, S.; Zhou, W.; Ruotsalainen, S.; Pärn, K.; Hiekkalinna, T.; Koskelainen, S.; Paajanen, T.; Llorens, V.; Gracia-Tabuenca, J.; Siirtola, H.; Reis, K.; Elnahas, A. G.; Sun, B.; Foley, C. N.; Aalto-Setälä, K.; Alasoo, K.; Arvas, M.; Auro, K.; Biswas, S.; Bizaki-Vallaskangas, A.; Carpen, O.; Chen, C.-Y.; Dada, O. A.; Ding, Z.; Ehm, M. G.; Eklund, K.; Färkkilä, M.; Finucane, H.; Ganna, A.; Ghazal, A.; Graham, R. R.; Green, E. M.; Hakanen, A.; Hautalahti, M.; Hedman, Å. K.; Hiltunen, M.; Hinttala, R.; Hovatta, I.; Hu, X.; Huertas-Vazquez, A.; Huilaja, L.; Hunkapiller, J.; Jacob, H.; Jensen, J.-N.; Joensuu, H.; John, S.; Julkunen, V.; Jung, M.; Junttila, J.; Kaarniranta, K.; Kähönen, M.; Kajanne, R.; Kallio, L.; Kälviäinen, R.; Kaprio, J.; Kerimov, N.; Kettunen, J.; Kilpeläinen, E.; Kilpi, T.; Klinger, K.; Kosma, V.-M.; Kuopio, T.; Kurra, V.; Laisk, T.; Laukkanen, J.; Lawless, N.; Liu, A.; Longerich, S.; Mägi, R.; Mäkelä, J.; Mäkitie, A.; Malarstig, A.; Mannermaa, A.; Maranville, J.; Matakidou, A.; Meretoja, T.; Mozaffari, S. V.; Niemi, M. E. K.; Niemi, M.; Niiranen, T.; O Donnell, C. J.; Obeidat, M. E.; Okafo, G.; Ollila, H. M.; Palomäki, A.; Palotie, T.; Partanen, J.; Paul, D. S.; Pelkonen, M.; Pendergrass, R. K.; Petrovski, S.; Pitkäranta, A.; Platt, A.; Pulford, D.; Punkka, E.; Pussinen, P.; Raghavan, N.; Rahimov, F.; Rajpal, D.; Renaud, N. A.; Riley-Gillis, B.; Rodosthenous, R.; Saarentaus, E.; Salminen, A.; Salminen, E.; Salomaa, V.; Schleutker, J.; Serpi, R.; Shen, H.-Y.; Siegel, R.; Silander, K.; Siltanen, S.; Soini, S.; Soininen, H.; Sul, J. H.; Tachmazidou, I.; Tasanen, K.; Tienari, P.; Toppila-Salmi, S.; Tukiainen, T.; Tuomi, T.; Turunen, J. A.; Ulirsch, J. C.; Vaura, F.; Virolainen, P.; Waring, J.; Waterworth, D.; Yang, R.; Nelis, M.; Reigo, A.; Metspalu, A.; Milani, L.; Esko, T.; Fox, C.; Havulinna, A. S.; Perola, M.; Ripatti, S.; Jalanko, A.; Laitinen, T.; Mäkelä, T. P.; Plenge, R.; McCarthy, M.; Runz, H.; Daly, M. J.; Palotie, A., FinnGen provides genetic insights from a well-phenotyped isolated population. Nature 2023, 613 (7944), 508-518. Eyoum Bille, B. B.; Kouitcheu Mabeku, L. B., Relationship between active Helicobacter pylori infection and anemia, iron deficiency, iron deficiency anemia: A cross-sectional study in a sub-Saharan setting. JGH Open : an Open Access Journal of Gastroenterology and Hepatology 2022, 6 (8), 554-568. Hudak, L.; Jaraisy, A.; Haj, S.; Muhsen, K., An updated systematic review and meta-analysis on the association between Helicobacter pylori infection and iron deficiency anemia. Helicobacter 2017, 22 (1). Ulasoglu, C.; Temiz, H. E.; Sağlam, Z. A., The Relation of Cytotoxin-Associated Gene-A Seropositivity with Vitamin B12 Deficiency in Helicobacter pylori-Positive Patients. BioMed Research International 2019, 2019 , 1450536. Gökışık, M. T.; Uyar, S., The role of Helicobacter pylori in vitamin-B12 deficiency due to metformin use. Helicobacter 2020, 25 (5), e12718. Lee, J. Y.; Kim, S. E.; Park, S. J.; Park, M. I.; Moon, W.; Kim, J. H.; Jung, K., Helicobacter pylori infection and iron deficiency in non-elderly adults participating in a health check-up program. The Korean Journal of Internal Medicine 2022, 37 (2), 304-312. Mendoza, E.; Duque, X.; Hernández Franco, J. I.; Reyes Maldonado, E.; Morán, S.; Martínez, G.; Salinas Rodríguez, A.; Martínez, H., Association between Active H. pylori Infection and Iron Deficiency Assessed by Serum Hepcidin Levels in School-Age Children. Nutrients 2019, 11 (9). Pinar, I. E.; Mavis, O., The Effect of Helicobacter pylori Density on Serum Vitamin B12 and Folate Levels in Patients With Non-atrophic Gastritis. Cureus 2023, 15 (9), e45252. Katelaris, P.; Hunt, R.; Bazzoli, F.; Cohen, H.; Fock, K. M.; Gemilyan, M.; Malfertheiner, P.; Mégraud, F.; Piscoya, A.; Quach, D.; Vakil, N.; Vaz Coelho, L. G.; LeMair, A.; Melberg, J., Helicobacter pylori World Gastroenterology Organization Global Guideline. Journal of Clinical Gastroenterology 2023, 57 (2), 111-126. Viazis, N.; Argyriou, K.; Kotzampassi, K.; Christodoulou, D. K.; Apostolopoulos, P.; Georgopoulos, S. D.; Liatsos, C.; Giouleme, O.; Koustenis, K.; Veretanos, C.; Stogiannou, D.; Moutzoukis, M.; Poutakidis, C.; Mylonas, I. I.; Tseti, I.; Mantzaris, G. J., A Four-Probiotics Regimen Combined with A Standard Helicobacter pylori-Eradication Treatment Reduces Side Effects and Increases Eradication Rates. Nutrients 2022, 14 (3). Chen, W.; Shi, S.; Tu, J.; Liao, L.; Liao, Y.; Chen, K.; Chen, L.; Huang, R., Nutrition-related diseases and cardiovascular mortality in American society: national health and nutrition examination study, 1999-2006. BMC Public Health 2022, 22 (1), 1849. Li, Y.; Choi, H.; Leung, K.; Jiang, F.; Graham, D. Y.; Leung, W. K., Global prevalence of Helicobacter pylori infection between 1980 and 2022: a systematic review and meta-analysis. The Lancet. Gastroenterology & Hepatology 2023, 8 (6), 553-564. Additional Declarations No competing interests reported. Supplementary Files SupplementaryTableS1.xlsx SupplementaryTableS2.xlsx SupplementaryTableS3.xlsx Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-3940357","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":273877999,"identity":"0d7f9c0d-077d-4f9a-9b0f-57feac60b6f6","order_by":0,"name":"Chuqi Xia","email":"","orcid":"","institution":"Second Affiliated Hospital of Kunming Medical College","correspondingAuthor":false,"prefix":"","firstName":"Chuqi","middleName":"","lastName":"Xia","suffix":""},{"id":273878000,"identity":"ce04eb66-f157-4458-9937-fc11ec548c59","order_by":1,"name":"Wanyang Lei","email":"","orcid":"","institution":"Second Affiliated Hospital of Kunming Medical College","correspondingAuthor":false,"prefix":"","firstName":"Wanyang","middleName":"","lastName":"Lei","suffix":""},{"id":273878001,"identity":"81cb80a8-115d-4f7b-9da0-b1c0d7bec75b","order_by":2,"name":"Yongyu Yang","email":"","orcid":"","institution":"Second Affiliated Hospital of Kunming Medical College","correspondingAuthor":false,"prefix":"","firstName":"Yongyu","middleName":"","lastName":"Yang","suffix":""},{"id":273878002,"identity":"58d3af3a-ee94-4156-9964-df0c221eb5e7","order_by":3,"name":"Guowu Sun","email":"","orcid":"","institution":"Second Affiliated Hospital of Kunming Medical College","correspondingAuthor":false,"prefix":"","firstName":"Guowu","middleName":"","lastName":"Sun","suffix":""},{"id":273878003,"identity":"58f09764-ff4b-404b-9470-e7158f3c916a","order_by":4,"name":"Yang Zhang","email":"","orcid":"","institution":"Affiliated Cardiovascular Hospital of Kunming Medical University","correspondingAuthor":false,"prefix":"","firstName":"Yang","middleName":"","lastName":"Zhang","suffix":""},{"id":273878004,"identity":"f380c90f-9f2c-421e-b2d7-bce0ad1f3d0a","order_by":5,"name":"Xinyue Li","email":"","orcid":"","institution":"Kunming Medical University","correspondingAuthor":false,"prefix":"","firstName":"Xinyue","middleName":"","lastName":"Li","suffix":""},{"id":273878005,"identity":"a5ce4afe-977d-4071-a536-3279421f9f6f","order_by":6,"name":"Ning Xu","email":"","orcid":"","institution":"Second Affiliated Hospital of Kunming Medical College","correspondingAuthor":false,"prefix":"","firstName":"Ning","middleName":"","lastName":"Xu","suffix":""},{"id":273878006,"identity":"554d6b5d-0491-4303-b37d-d0b151a1a537","order_by":7,"name":"Daoming Liang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA/UlEQVRIiWNgGAWjYDCCA0CcwMAgwwakGRsYbBjYiNXCA9WSRqQWIOBhgGg5TNhdfMcPH93wcEctDx/72cMvZ+act+eTbn7A8KNiG04tkmfS0m4knjnOw8aTl2a5cdvtxDaZYwaMPWdu49RicCDH7EZi2zGgX3LMDB9uu53AJpFgwMzYhkfL+TdQLfxvQFrO2bNJpH/Ar+UG2JYaHjaJHOOHG7cdYGyTyMFvi+SNZ0C/tB0AanljxjhzW3IiUEvBQXx+4TuffOzmz7Y6Ofn+HOOPvdvs7OVnpG988KMCtxYoAEcHmwSMe4CQeiCoAxHMH4hQOQpGwSgYBSMQAABE4V0riOQccwAAAABJRU5ErkJggg==","orcid":"","institution":"Second Affiliated Hospital of Kunming Medical College","correspondingAuthor":true,"prefix":"","firstName":"Daoming","middleName":"","lastName":"Liang","suffix":""}],"badges":[],"createdAt":"2024-02-08 15:18:45","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-3940357/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-3940357/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":51470389,"identity":"90536047-5c7b-4f57-a670-4ca351529eb3","added_by":"auto","created_at":"2024-02-22 07:45:00","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":687251,"visible":true,"origin":"","legend":"\u003cp\u003eThree assumptions and flowchart of our bidirectional two-sample MR analysis. (A) Schematic diagram of the MR assumptions underpinning a MR analysis; (B, C) Flowchart of the bidirectional MR study on the causal effects of \u003cem\u003eH. pylori\u003c/em\u003e infection on anemia, IDA, and vitamin B12 deficiency anemia among European individuals. SNPs: single-nucleotide polymorphisms, HP: \u003cem\u003eHelicobacter pylori\u003c/em\u003e, GWAS: Genome-Wide Association Studies, IDA: iron deficiency anemia.\u003c/p\u003e","description":"","filename":"Figure1.flowchart.png","url":"https://assets-eu.researchsquare.com/files/rs-3940357/v1/ff9eb9b382550c2112c9c23c.png"},{"id":51470388,"identity":"a6b94521-248a-4be8-bdf3-1236f049cd17","added_by":"auto","created_at":"2024-02-22 07:45:00","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":318310,"visible":true,"origin":"","legend":"\u003cp\u003eEstimated causal effects between H. pylori infection and anemia using IVW.\u003c/p\u003e","description":"","filename":"Figure2.forestplot.png","url":"https://assets-eu.researchsquare.com/files/rs-3940357/v1/59650ebf95684d794ee8f2e0.png"},{"id":53386949,"identity":"2c022251-aed0-4e20-9b53-a2de4ae6c4de","added_by":"auto","created_at":"2024-03-25 11:32:12","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1013914,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3940357/v1/7abe36d6-0e3e-4a32-82d6-4a8a4048fe90.pdf"},{"id":51470391,"identity":"a191bb92-403a-4b40-bfe6-fa05f7502fb1","added_by":"auto","created_at":"2024-02-22 07:45:00","extension":"xlsx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":14712,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementaryTableS1.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-3940357/v1/119d5a136958f466b14cdd54.xlsx"},{"id":51470392,"identity":"cf5e9a7b-9dc1-4b06-a6fe-76fd94e0d66d","added_by":"auto","created_at":"2024-02-22 07:45:00","extension":"xlsx","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":15710,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementaryTableS2.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-3940357/v1/1aedf4835e0e6643e74784a5.xlsx"},{"id":51470390,"identity":"933437d0-ffd4-41ac-8144-d87eafd6cb28","added_by":"auto","created_at":"2024-02-22 07:45:00","extension":"xlsx","order_by":3,"title":"","display":"","copyAsset":false,"role":"supplement","size":13610,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementaryTableS3.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-3940357/v1/efa0900d923074e42f3d5979.xlsx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Associations of Helicobacter Pylori with Anemia: A Bidirectional Two-Sample Mendelian Randomization Study","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003e \u003cem\u003eHelicobacter pylori\u003c/em\u003e, a gram-negative, microaerophilic bacterium predominantly inhabiting the gastric epithelium, has been unequivocally implicated in a plethora of gastroduodenal pathologies, most notably peptic ulcer disease and gastric adenocarcinoma\u003csup\u003e1, 2\u003c/sup\u003e. The organism's role in these conditions has been well-characterized, and bolstered by decades of rigorous scientific inquiry. However, recent studies have expanded the understanding of the influence of \u003cem\u003eH. pylori\u003c/em\u003e, highlighting its association with diseases beyond the gastroduodenal system, including iron deficiency anemia (IDA), immune thrombocytopenic purpura, vitamin B12 deficiency, metabolic syndrome, diabetes mellitus and so on\u003csup\u003e3\u003c/sup\u003e. Various pathogenic mechanisms, including the occurrence of molecular mimicry and the induction of low-grade inflammation, have been hypothesized\u003csup\u003e4\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eIt is well known that \u003cem\u003eH. pylori\u003c/em\u003e infection can induce chronic gastritis, resulting in gastric mucosa damage, which may affect the absorption of nutrients such as vitamin B12 and iron\u003csup\u003e5\u003c/sup\u003e. Therefore, significant research interest has been directed toward the association between \u003cem\u003eH. pylori\u003c/em\u003e infections and nutritional anemia. To our knowledge, a growing body of observational studies has reported an association between \u003cem\u003eH. pylori\u003c/em\u003e infection and the higher prevalence of anemia, iron deficiency, IDA, vitamin B12 deficiency, and vitamin B12 deficiency anemia\u003csup\u003e6, 7\u003c/sup\u003e. A meta-analysis of 15 case-control studies revealed a substantial increase in IDA risk among \u003cem\u003eH. pylori\u003c/em\u003e-infected patients, with an odds ratio (OR) of 2.2 (95% CI:1.5\u0026ndash;3.2)\u003csup\u003e8\u003c/sup\u003e. This link is believed to originate from \u003cem\u003eH. pylori-\u003c/em\u003einduced chronic gastritis, leading to gastric mucosal damage and occult blood loss, resulting in iron deficiency and IDA\u003csup\u003e9\u003c/sup\u003e. Additionally, Sarari et al. reported vitamin B12 deficiency in 67.4% of \u003cem\u003eH. pylori\u003c/em\u003e-infected patients\u003csup\u003e10\u003c/sup\u003e, likely due to gastritis-induced atrophic changes in the gastric mucosa, impairing vitamin B12 absorption\u003csup\u003e11\u003c/sup\u003e. These associations, while supported by epidemiological data, remain speculative due to observational studies' limitations, such as confounding variables and inability to establish causality.\u003c/p\u003e \u003cp\u003eIn this regard, Mendelian randomization (MR) has emerged as a valuable tool for exploring the causal effects of \u003cem\u003eH. pylori\u003c/em\u003e infection on anemia. Using genetic variants (single nucleotide polymorphisms, SNPs) as instrumental variables (IVs), MR circumvents the typical confounders of observational research and overcomes reverse causation bias\u003csup\u003e12\u003c/sup\u003e. Studies using MR have offered new insights into the impact of \u003cem\u003eH. pylori\u003c/em\u003e on various diseases. For instance, Chen et al.\u003csup\u003e13\u003c/sup\u003e identified a link between \u003cem\u003eH. pylori\u003c/em\u003e IgG antibodies and an increased risk of gastroesophageal reflux disease, while Liu et al.\u003csup\u003e14\u003c/sup\u003e found no genetic evidence for a causal relationship between \u003cem\u003eH. pylori\u003c/em\u003e and nonalcoholic fatty liver disease. These findings highlight the potential of MR to inform prevention and treatment strategies for \u003cem\u003eH. pylori\u003c/em\u003e infection.\u003c/p\u003e \u003cp\u003eTherefore, we employed a bidirectional two-sample MR approach to delve deeper into the causal relationship between \u003cem\u003eH. pylori\u003c/em\u003e infection and anemia. Considering the findings from previous observational studies and the limitations of available database resources, the data for SNPs associated with anemia, IDA, and vitamin B12 deficiency anemia from the latest release of the FinnGen Biobank (R10, December 2023) were chosen in our research. Meanwhile, SNPs associated with susceptibility to \u003cem\u003eH. pylori\u003c/em\u003e infection were identified through literature search or genome-wide association studies (GWAS) summary data analysis, involving data on \u003cem\u003eH. pylori\u003c/em\u003e seropositivity, anti-\u003cem\u003eH. pylori\u003c/em\u003e CagA, VacA, and IgG levels. Our goal is to elucidate potential genetic mechanisms linking \u003cem\u003eH. pylori\u003c/em\u003e infection to anemia, IDA, and vitamin B12 deficiency anemia, providing a foundation for disease prevention strategies.\u003c/p\u003e"},{"header":"2. Materials and Methods","content":"\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.1. Study Design and Framework\u003c/h2\u003e \u003cp\u003eThis investigation employs a two-sample bidirectional MR framework, utilizing SNPs as IVs to explore the causal effects of \u003cem\u003eH. pylori\u003c/em\u003e infection on anemia, IDA, and vitamin B12 deficiency anemia. Three assumptions must be met to confirm the validity of MR analysis: (1) genetic variants directly affect the risk factor; (2) genetic variants are not associated with any known or unknown confounders; and (3) genetic variants affect the outcome through only the risk factor and not through other pathways. For a detailed discussion of these assumptions, refer to Greenland\u003csup\u003e15\u003c/sup\u003e. Figure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e presents a schematic diagram summarizing the MR assumptions and a flowchart illustrating our bidirectional two-sample MR analysis. The datasets used in this study are available from public databases and received ethical approval before implementation. This study, therefore, did not require additional ethical approval.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.2. Data Source and Study Population\u003c/h2\u003e \u003cp\u003eSNPs associated with susceptibility to \u003cem\u003eH. pylori\u003c/em\u003e infection were identified via either a literature search or a GWAS summary data analysis. The data for SNPs associated with \u003cem\u003eH. pylori\u003c/em\u003e infection were composed of \u003cem\u003eH. pylori\u003c/em\u003e seropositivity, \u003cem\u003eanti-H. pylori\u003c/em\u003e CagA, anti-\u003cem\u003eH. pylori\u003c/em\u003e VacA, and anti-\u003cem\u003eH. pylori\u003c/em\u003e IgG. SNPs associated with \u003cem\u003eH. pylori\u003c/em\u003e infection were identified in a study conducted by Mayerle et al.\u003csup\u003e16\u003c/sup\u003e on a European population that included 2763 cases and 8175 controls. SNPs associated with anti-\u003cem\u003eH. pylori\u003c/em\u003e CagA from the European Bioinformatics Institute (EBI) database included 985 samples with 9,165,056 SNPs\u003csup\u003e17\u003c/sup\u003e. SNPs associated with anti-\u003cem\u003eH. pylori\u003c/em\u003e VacA from the GWAS meta-analysis of EBI data included 1,571 samples with 9,178,635 SNPs\u003csup\u003e17\u003c/sup\u003e. Similarly, SNPs associated with \u003cem\u003eH. pylori\u003c/em\u003e IgG seropositivity according to the GWAS meta-analysis of EBI data included 4,683 samples with 7,247,045 SNPs. Further information about OpenGWAS can be found at \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://gwas.mrcieu.ac.uk/\u003c/span\u003e\u003cspan address=\"https://gwas.mrcieu.ac.uk/\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/p\u003e \u003cp\u003eTo prevent participant overlap, genomic data on anemia traits were obtained from the FinnGen Biobank (R10). In the FinnGen consortium, anemia included 30,092 cases and 94,450 controls of European ancestry, IDA included 15,153 cases and 393,684 controls of European ancestry, vitamin B12 deficiency anemia included 3,694 cases and 393,684 controls of European ancestry\u003csup\u003e18\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eAll participants were of European ancestry. All the original studies obtained ethical approval and informed consent. The details of the included GWASs are summarized in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eDetails of the studies in the mendelian randomization analysis. HP: Helico-bacter pylori, EBI: European Bioinformatics Institute, IDA: iron deficiency anemia, VB12DA: vitamin B12 deficiency anemia.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eExposure or outcome\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eConsortium or author\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003ePopulation\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSample size\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eYear\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eWeb source\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHP infection\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMayerle et al.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eEuropean\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e10,938\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e2013\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://jamanetwork.com/journals/jama/fullarticle/1685857\u003c/span\u003e\u003cspan address=\"https://jamanetwork.com/journals/jama/fullarticle/1685857\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAnti-HP CagA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eEBI\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eEuropean\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e985\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e2020\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://gwas.mrcieu.ac.uk/datasets/ebi-a-GCST90006911/\u003c/span\u003e\u003cspan address=\"https://gwas.mrcieu.ac.uk/datasets/ebi-a-GCST90006911/\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAnti-HP VacA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eEBI\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eEuropean\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1,571\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e2020\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://gwas.mrcieu.ac.uk/datasets/ebi-a-GCST90006916/\u003c/span\u003e\u003cspan address=\"https://gwas.mrcieu.ac.uk/datasets/ebi-a-GCST90006916/\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAnti-HP IgG\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eEBI\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eEuropean\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e4,683\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e2021\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://gwas.mrcieu.ac.uk/datasets/ieu-b-4905/\u003c/span\u003e\u003cspan address=\"https://gwas.mrcieu.ac.uk/datasets/ieu-b-4905/\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAnemia\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eFinngen (R10)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eEuropean\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e124,542\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e2023\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://storage.googleapis.com/finngen-public-data-r10/summary_stats/finngen_R10_D3_ANAEMIA.gz\u003c/span\u003e\u003cspan address=\"https://storage.googleapis.com/finngen-public-data-r10/summary_stats/finngen_R10_D3_ANAEMIA.gz\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIDA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eFinngen (R10)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eEuropean\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e408,837\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e2023\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://storage.googleapis.com/finngen-public-data-r10/summary_stats/finngen_R10_D3_ANAEMIA_IRONDEF.gz\u003c/span\u003e\u003cspan address=\"https://storage.googleapis.com/finngen-public-data-r10/summary_stats/finngen_R10_D3_ANAEMIA_IRONDEF.gz\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVB\u003csub\u003e12\u003c/sub\u003eDA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eFinngen (R10)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eEuropean\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e397,378\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e2023\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://storage.googleapis.com/finngen-public-data-r10/summary_stats/finngen_R10_D3_ANAEMIA_B12_DEF.gz\u003c/span\u003e\u003cspan address=\"https://storage.googleapis.com/finngen-public-data-r10/summary_stats/finngen_R10_D3_ANAEMIA_B12_DEF.gz\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.3. Instrumental Variable Selection and Validation\u003c/h2\u003e \u003cp\u003eWe conducted a series of stringent quality control measures to select IVs that adhere to the three fundamental assumptions of MR analysis, thereby ensuring its robustness and reliability. Initially, genetic variants linked to the exposure were pinpointed at the genome-wide significance level (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;5 \u0026times; 10\u003csup\u003e\u0026minus;\u0026thinsp;8\u003c/sup\u003e). If an adequate number of IVs are not found at this threshold, a more relaxed threshold (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;5 \u0026times; 10\u003csup\u003e\u0026minus;\u0026thinsp;6\u003c/sup\u003e) will be adopted. Two SNPs, rs10004195 and rs368433, identified in Mayerle et al.'s\u003csup\u003e16\u003c/sup\u003e study as independently and strongly linked to \u003cem\u003eH. pylori\u003c/em\u003e seropositivity, were classified as IVs. Secondly, any SNP significantly associated with the outcome was excluded. Thirdly, SNPs were clumped with a threshold of r\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.001 and a window size of 10mb assessed in the European 1,000 genomes reference panel. Fourth, SNPs potentially demonstrating pleiotropic effects were eliminated. Specifically, we utilized the MR Pleiotropy Residual Sum and Outlier (MR-PRESSO) method to assess outliers for pleiotropy. Fifth, we calculated the F statistic \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\((\\varvec{F}={\\varvec{b}\\varvec{e}\\varvec{t}\\varvec{a}}^{2}/{\\varvec{s}\\varvec{e}}^{2})\\)\u003c/span\u003e\u003c/span\u003e to address potential bias from weak IVs; an F statistic less than 10 suggested an invalid IV. Ambiguous and palindromic SNPs were harmonized to ensure accuracy.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e2.4. Statistical analyses\u003c/h2\u003e \u003cp\u003eWe utilized a bidirectional two-sample MR approach to investigate the causal relationship. The foundation of our study was inverse variance weighted (IVW) analysis, which acted as the principal method of analysis. In the presence of potential heterogeneity among the analyzed SNPs, our analysis employed a random-effects inverse-variance model. We also adopted complementary methods, such as MR-Egger and weighted median analyses. Notably, to tackle the issue of multiple testing, we adopted a conservative Bonferroni-corrected threshold (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;2.38 \u0026times; 10\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e), because 21 causalities were evaluated for this bidirectional analysis. The MR analysis was performed using the R software environment (version 4.3.1), utilizing the TwoSampleMR (version 0.5.7) and MRPRESSO (version 1.0) packages.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e2.5. Sensitivity analyses\u003c/h2\u003e \u003cp\u003eA multistep process was conducted for sensitivity analysis and to assess the second and third assumptions. Initially, Cochran\u0026rsquo;s Q test was used to evaluate heterogeneity among the IVs. Subsequently, the MR-Egger regression was employed to assess the potential horizontal pleiotropy of the IVs.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results","content":"\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Instrumental Variables\u003c/h2\u003e \u003cp\u003eTo analyze the effects of H. pylori infection on anemia, IDA, and vitamin B12 deficiency anemia. Firstly, two SNPs (rs10004195 and rs368433) from the study by Mayerle et al.\u003csup\u003e16\u003c/sup\u003e were identified as independent and strongly associated with H. pylori seropositivity, and were regarded as IVs. The F-statistics for these IVs were 81 and 26.69, respectively, effectively avoiding the impact of weak IVs on the causal effect. We subsequently selected 15 SNPs for H. pylori CagA antibody levels, 15 SNPs for H. pylori VacA antibody levels, and 12 SNPs for anti-H. pylori IgG levels as IVs with a genome-wide significance of \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;5 \u0026times; 10\u003csup\u003e\u0026minus;\u0026thinsp;6\u003c/sup\u003e. To analyze the effects of anemia, IDA, and vitamin B12 deficiency anemia on H. pylori infection, we selected at least 2 and up to 13 SNPs for anemia, IDA, and vitamin B12 deficiency anemia as IVs with a genome-wide significance of \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;5 \u0026times; 10\u003csup\u003e\u0026minus;\u0026thinsp;8\u003c/sup\u003e. Several analyses were unsuccessful due to the absence of SNPs post-harmonization. The F-statistic for IVs suggested that the estimates were unlikely to suffer from weak instrumental bias (F\u0026thinsp;\u0026gt;\u0026thinsp;10). The detailed information of IVs of exposures is presented in Supplementary Table \u003cspan refid=\"MOESM2\" class=\"InternalRef\"\u003eS2\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003cb\u003e3.2 Causal effect of\u003c/b\u003e \u003cb\u003eH. pylori\u003c/b\u003e \u003cb\u003einfection on Anemia, Iron Deficiency Anemia, and Vitamin B12 deficiency anemia\u003c/b\u003e\u003c/p\u003e \u003cp\u003eThe results of MR estimates using IVW are presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. And other different several philosophies are presented in Supplementary Table \u003cspan refid=\"MOESM2\" class=\"InternalRef\"\u003eS2\u003c/span\u003e. There was no evidence of a causal connection between having a genetic predisposition to \u003cem\u003eH. pylori\u003c/em\u003e infection and an increased risk of anemia, IDA, or vitamin B12 deficiency anemia. The primary IVW method showed that genetically predicted H. pylori seropositivity in Mayerle et al.\u0026rsquo;s\u003csup\u003e16\u003c/sup\u003e study was not causally associated with anemia [OR\u0026thinsp;=\u0026thinsp;0.97, 95% confidence interval (CI): 0.91\u0026ndash;1.05, p\u0026thinsp;=\u0026thinsp;0.49], with IDA (OR\u0026thinsp;=\u0026thinsp;0.96, 95% CI: 0.89\u0026ndash;1.03, p\u0026thinsp;=\u0026thinsp;0.24), or with vitamin B12 deficiency anemia (OR\u0026thinsp;=\u0026thinsp;0.88, 95% CI: 0.72\u0026ndash;1.08, p\u0026thinsp;=\u0026thinsp;0.22) in FinnGen Biobank (R10). In addition, the MR estimates showed that the causal effect of anti-H. pylori CagA, VacA, and IgG levels on anemia and its subtypes was the same as that of \u003cem\u003eH. pylori\u003c/em\u003e infection on anemia (p\u0026thinsp;\u0026gt;\u0026thinsp;2.38 \u0026times; 10\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e, Bonferroni-corrected threshold). The direction is consistent across sensitivity analyses, including MR-Egger and weighted median. Notably, the results of genetic causal effect of anti-\u003cem\u003eH. pylori\u003c/em\u003e CagA (OR\u0026thinsp;=\u0026thinsp;0.93, 95% CI: 0.87-1.00, p\u0026thinsp;=\u0026thinsp;0.04) and anti-\u003cem\u003eH. pylori\u003c/em\u003e IgG (OR\u0026thinsp;=\u0026thinsp;0.90, 95% CI: 0.83\u0026ndash;0.98, p\u0026thinsp;=\u0026thinsp;0.01) on an increased risk of IDA ranged 2.38 \u0026times; 10\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e and 0.05, which implies that there may be a potential causal effect of anti-H. pylori CagA and IgG levels on a reduced risk of IDA.\u003c/p\u003e \u003cp\u003e \u003cb\u003e3.3 Causal effect of Anemia, Iron Deficiency Anemia, and Vitamin B12 Deficiency Anemia on\u003c/b\u003e \u003cb\u003eH. pylori\u003c/b\u003e \u003cb\u003einfection\u003c/b\u003e\u003c/p\u003e \u003cp\u003eThe IVW results showed that genetically predicted anemia and its subtypes had no genetic causal relationship with \u003cem\u003eH. pylori\u003c/em\u003e infection (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026gt;\u0026thinsp;0.05) (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, Supplementary Table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e). Anemia was not causally associated with anti-\u003cem\u003eH. pylori\u003c/em\u003e CagA (OR\u0026thinsp;=\u0026thinsp;1.01, 95% CI: 0.67\u0026ndash;1.54, p\u0026thinsp;=\u0026thinsp;0.95), with anti-H. pylori VacA (OR\u0026thinsp;=\u0026thinsp;0.89, 95% CI: 0.69\u0026ndash;1.15, p\u0026thinsp;=\u0026thinsp;0.37), or with anti-\u003cem\u003eH. pylori\u003c/em\u003e IgG (OR\u0026thinsp;=\u0026thinsp;1.38, 95% CI: 1.00-1.90, p\u0026thinsp;=\u0026thinsp;0.05); IDA was not causally associated with anti-\u003cem\u003eH. pylori\u003c/em\u003e CagA (OR\u0026thinsp;=\u0026thinsp;0.92, 95% CI: 0.65\u0026ndash;1.31, p\u0026thinsp;=\u0026thinsp;0.64), with anti-\u003cem\u003eH. pylori\u003c/em\u003e VacA (OR\u0026thinsp;=\u0026thinsp;1.04, 95% CI: 0.78\u0026ndash;1.40, p\u0026thinsp;=\u0026thinsp;0.79), or with anti-\u003cem\u003eH. pylori\u003c/em\u003e IgG (OR\u0026thinsp;=\u0026thinsp;1.09, 95% CI: 0.89\u0026ndash;1.32, p\u0026thinsp;=\u0026thinsp;0.41); vitamin B12 deficiency anemia was also not causally associated with anti-\u003cem\u003eH. pylori\u003c/em\u003e CagA (OR\u0026thinsp;=\u0026thinsp;0.88, 95% CI: 0.74\u0026ndash;1.04, p\u0026thinsp;=\u0026thinsp;0.12), with anti-\u003cem\u003eH. pylori\u003c/em\u003e VacA (OR\u0026thinsp;=\u0026thinsp;0.94, 95% CI: 0.84\u0026ndash;1.05, p\u0026thinsp;=\u0026thinsp;0.29), or with anti-\u003cem\u003eH. pylori\u003c/em\u003e IgG (OR\u0026thinsp;=\u0026thinsp;1.04, 95% CI: 0.92\u0026ndash;1.18, p\u0026thinsp;=\u0026thinsp;0.54). The sensitivity analyses of both weighted median approach and the MR-Egger method generated identical results.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e3.4 Sensitivity analyses\u003c/h2\u003e \u003cp\u003eAll P values from the Cochran Q tests exceeded 0.05, signifying a lack of observable heterogeneity. Insufficient evidence was found for horizontal pleiotropy, as all P values from subsequent Egger intercept exceeded 0.05. Sensitivity analysis results are presented in Supplementary Table \u003cspan refid=\"MOESM2\" class=\"InternalRef\"\u003eS2\u003c/span\u003e.\u003c/p\u003e \u003c/div\u003e"},{"header":"4. Discussion","content":"\u003cp\u003eIn this study, we refrained from directly comparing \u003cem\u003eH. pylori\u003c/em\u003e serology with anemia, IDA and vitamin B12 deficiency anemia. Instead, we adopted a bidirectional MR approach by using potential SNPs associated with \u003cem\u003eH. pylori\u003c/em\u003e infection from four genetic data pools as IVs. To provide additional context, we referenced prior research, including the study by Mayerle et al.\u003csup\u003e16\u003c/sup\u003e. Meanwhile, SNPs associated with anemia were identified from three genetic data pools from the latest release of the FinnGen Biobank (R10, December 2023). This approach aimed to evaluate the potential causal relationship between \u003cem\u003eH. pylori\u003c/em\u003e and anemia. Our results suggest that there is no causal effect of genetic predisposition to \u003cem\u003eH. pylori\u003c/em\u003e infection on the risk of anemia, IDA, and vitamin B12 deficiency anemia. This consistency in results persisted across various MR sensitivity analysis methods. While acknowledging that factors such as hygiene standards and family history influence \u003cem\u003eH. pylori\u003c/em\u003e infection, we also recognize the need for further replication and validation of the identified SNPs as surrogate biomarkers for predicting \u003cem\u003eH. pylori\u003c/em\u003e infection. Nonetheless, our primary objective was to delve into the potential genetic factors associated with this relationship, thereby enhancing our understanding of the biology of \u003cem\u003eH. pylori\u003c/em\u003e-related nutrition-related diseases. This section provides an in-depth analysis, situating our findings within the existing body of research.\u003c/p\u003e \u003cp\u003eTo our knowledge, there is no inconsistent evidence on the association of \u003cem\u003eH. pylori\u003c/em\u003e infection with an increased risk of anemia, IDA, and vitamin B12 deficiency. A large cross-sectional study conducted by Eyoum Bille et al.\u003csup\u003e19\u003c/sup\u003e in 2022 revealed that compared with \u003cem\u003eH. pylori\u003c/em\u003e non-infected participants, \u003cem\u003eH. pylori\u003c/em\u003e infected patients were 1.2938 (95%CI: 0.9087\u0026ndash;1.8421), 1.1851 (95%CI: 0.8122\u0026ndash;1.7292), and 1.5636 (95%CI: 1.0206\u0026ndash;2.3953) times at higher risk to develop anemia, iron deficiency, and IDA, respectively, and a significant relationship was found between \u003cem\u003eH. pylori\u003c/em\u003e infection and IDA (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.04). A lastest meta-analysis of 14 observational studies by Hudak et al.\u003csup\u003e20\u003c/sup\u003e reported similar conclusion: compared to uninfected persons, \u003cem\u003eH. pylori\u003c/em\u003e-infected individuals showed an increased likelihood of IDA. A well-recognized explanation for this phenomenon is that \u003cem\u003eH. pylori\u003c/em\u003e chronic gastritis can change the physiology of the stomach, inducing reductions in gastric acid secretion and gastric ascorbic acid levels, which are essential for the absorption of dietary iron\u003csup\u003e20\u003c/sup\u003e. Many studies have also shown a relationship between \u003cem\u003eH. pylori\u003c/em\u003e infection and vitamin B12 deficiency. In 2019, Ulasoglu et al.\u003csup\u003e21\u003c/sup\u003e found that cytotoxin-associated gene-A (CagA) seropositivity, which is one of the virulence factors of \u003cem\u003eH. pylori\u003c/em\u003e, was positively correlated with B12 deficiency. In 2020, a descriptive cross-sectional study conducted by G\u0026ouml;kışık et al.\u003csup\u003e22\u003c/sup\u003e, which included 421 patients, reached a similar conclusion: the rate of vitamin B12 deficiency was significantly higher among patients with \u003cem\u003eH. pylori\u003c/em\u003e infection. This may be due to the fact that a result of \u003cem\u003eH. pylori\u003c/em\u003e-induced gastritis and ulcers is destruction of the parietal cells which are important for the production of intrinsic factor which is essential for vitamin B12 absorption\u003csup\u003e10\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eNevertheless, a little scholarship supported that the absence of a correlation between \u003cem\u003eH. pylori\u003c/em\u003e infection and anemia. In 2022, Lee et al.\u003csup\u003e23\u003c/sup\u003e identified 1,069 non-elderly adults participating in a health check-up program, and found that there was no significant difference in anemia or IDA with \u003cem\u003eH. pylori\u003c/em\u003e In 2019, Mendoza et al.\u003csup\u003e24\u003c/sup\u003e performed a cross-sectional study on school-age children, and found that the association between \u003cem\u003eH. pylori\u003c/em\u003e and iron deficiency was not significant for lower values of hepcidin (OR\u0026thinsp;=\u0026thinsp;0.17; 95% CI: 0.02\u0026ndash;1.44). In 2023, Pinar et al.\u003csup\u003e25\u003c/sup\u003e also found that there was no relationship between the presence or density of \u003cem\u003eH. pylori\u003c/em\u003e with vitamin B12 levels. Meanwhile, most studies primarily assess \u003cem\u003eH. pylori\u003c/em\u003e status and measure serum vitamin B12 levels, yet there are no sufficient interventional studies demonstrating the impact of anti-\u003cem\u003eH. pylori\u003c/em\u003e therapy on vitamin B12 deficiency\u003csup\u003e3\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThere are a number of possible explanations for the controversy surrounding \u003cem\u003eH. pylori\u003c/em\u003e infection and the risk of nutrition-related diseases. First, there were no prospective, randomized, or blinded methods in any of these epidemiologic observational studies. Potential confounding factors might exist, including environmental and genetic factors. These confounders might simultaneously affect the onset and progression of \u003cem\u003eH. pylori\u003c/em\u003e infection, IDA and vitamin B12. Second, different studies have used different diagnostic strategies for \u003cem\u003eH. pylori\u003c/em\u003e infections and nutrition-related diseases. Based on the global guidelines of the World Gastroenterology Organization (WGO)\u003csup\u003e26\u003c/sup\u003e, the urine breath test is the most recommended non-invasive test to check for H. pylori infection. However, some studies measured \u003cem\u003eH. pylori\u003c/em\u003e infection using serum or IgG antibodies to \u003cem\u003eH. pylori\u003c/em\u003e or \u003cem\u003eH. pylori\u003c/em\u003e DNA sequences, and therefore, the criteria for the diagnosis of \u003cem\u003eH. pylori\u003c/em\u003e infection were inconsistent across studies\u003csup\u003e21, 24, 27\u003c/sup\u003e. Similarly, even though the World Health Organization (WHO) has established criteria for the diagnosis of malnutrition, there may be differences in diagnostic criteria and testing techniques across countries and regions\u003csup\u003e28\u003c/sup\u003e. Third, these differences could be attributed to differences in age, sex, geographic region, ethnicity, dietary habits, socioeconomic status, anti-\u003cem\u003eH. pylori\u003c/em\u003e IgG titers, and anti-\u003cem\u003eH. pylori\u003c/em\u003e antibody types and levels.\u003c/p\u003e \u003cp\u003eOur research is the first attempt to clarify the connection between \u003cem\u003eH. pylori\u003c/em\u003e infection and anemia from the perspective of genetic variation. Based on the thorough assumptions underpinning the relationship between genetic predisposition and outcome, in line with the principles of bidirectional MR, we found no convincing evidence to suggest a causal link between \u003cem\u003eH. pylori\u003c/em\u003e infection and the risk of anemia, IDA, or vitamin B12 deficiency anemia. Although randomized controlled trials are widely considered the most reliable approach for dentifying the presence of a causal relationship, it is not always possible to carry one out due to its high cost. However, since SNPs are randomly allocated at conception, MR studies can successfully correct for this potential confounding bias. Unlike the approaches used in other observational studies, MR offers the advantage of being able to address the reverse causality problem. Second, our study results may have implications for healthcare policies regarding \u003cem\u003eH. pylori\u003c/em\u003e infection and anemia. Given the high incidence of \u003cem\u003eH. pylori\u003c/em\u003e infection in the general population, establishing causation between \u003cem\u003eH. pylori\u003c/em\u003e infection and anemia can affect public health strategies for early prevention and appropriate intervention\u003csup\u003e29\u003c/sup\u003e. Our results indicate that anti-\u003cem\u003eH. pylori\u003c/em\u003e therapy may not be beneficial in the treatment of anemia, IDA, or vitamin B12 deficiency anemia. Consequently, this might contribute to significant reductions in public healthcare costs and the conservation of healthcare resources.\u003c/p\u003e \u003cp\u003eHowever, there are several limitations in our study. First, potential confounding factors and reverse causality might exist, and the diagnosis of \u003cem\u003eH. pylori\u003c/em\u003e infection was based on serological testing in the GWAS data, which may have biased on the detection of \u003cem\u003eH. pylori\u003c/em\u003e infection. And we can not ascertain the relative time of \u003cem\u003eH. pylori\u003c/em\u003e infection and anemia development when they collected the clinical samples, some pathophysiologic changes in anemia might exist and lead to \u003cem\u003eH. pylori\u003c/em\u003e infection before clinical diagnosis of anemia. Second, in our MR analysis, only two SNPs were signifcantly and independently linked to \u003cem\u003eH. pylori\u003c/em\u003e infection, while the remaining SNPs were associated with anti-HP CagA, Vac A, and IgG. These SNPs may not be perfect IVs and may lead to errors in the results. Third, MR is based on genetic variants, which reflects the long-term impact of \u003cem\u003eH. pylor\u003c/em\u003ei infection on anemia susceptibility across a lifetime. \u003cem\u003eH. pylor\u003c/em\u003ei infection is influenced by factors like hygiene standards and family history. Anemia, IDA, and vitamin B12 deficiency anemia is influenced by factors like dietary habit and nutrient intake. And the influence of \u003cem\u003eH. pylor\u003c/em\u003ei infection on anemia may vary significantly in the short term. Fourth, the databases employed were limited to European populations, constraining their generalizability to other racial groups.\u003c/p\u003e \u003cp\u003eIn summary, while we acknowledge the limitations and complexities of studying the association between \u003cem\u003eH. pylori\u003c/em\u003e and anemia, we believe that our study provides valuable insights by employing Mendelian randomization.\u003c/p\u003e"},{"header":"5. Conclusions","content":"\u003cp\u003eIn summary, this MR study contributes to the ongoing discourse on the systemic effects of \u003cem\u003eH. pylori\u003c/em\u003e infection by providing evidence against a direct genetic causal relationship with anemia, IDA, and vitamin B12 deficiency. This underscores the complexity of these conditions and the importance of using genetically informed methods to discern true causal relationships in epidemiological research.\u003c/p\u003e\n"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAuthor contributions:\u0026nbsp;\u003c/strong\u003eD.L. and N.X. designed the study. C.X. and W.L. analyzed the datasets and interpreted the results. G.S. and Y.Y. downloaded the data. Y.Z and X.L. provided software support. C.X. and W.L. wrote and edited the manuscript. D.L. provided the foundation and support. All the authors have read and agreed to the published version of the manuscript.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003cstrong\u003eFinancial:\u0026nbsp;\u003c/strong\u003eThis study is funded by\u0026nbsp;National Natural Science Foundation of China (8236030102) and\u0026nbsp;Joint Special Fund of Applied Fundamental Research of Kunming Medical University granted by\u0026nbsp;Science and Technology Office of Yunnan (202301AY070001-025).\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003cstrong\u003eInstitutional Review Board Statement:\u0026nbsp;\u003c/strong\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003cstrong\u003eInformed Consent Statement:\u0026nbsp;\u003c/strong\u003eThe data originated from a publicly accessible database, and as no human participants were involved, ethical parameters were deemed inapplicable.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003cstrong\u003eData Availability Statement:\u0026nbsp;\u003c/strong\u003eGWAS summary data of anemia, IDA, vitamin B12 deficiency anemia, anti-\u003cem\u003eH. pylori\u003c/em\u003e CagA, anti-\u003cem\u003eH. pylori\u003c/em\u003e VacA, and anti-\u003cem\u003eH. pylori\u003c/em\u003e IgG, \u0026nbsp; \u0026nbsp; were downloaded from FinnGen (R10) and IEU consortium. For \u003cem\u003eH. pylori\u0026nbsp;\u003c/em\u003eseropositivity, the GWAS summary data were selected from associated GWAS studies.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003cstrong\u003ePotential competing interests:\u0026nbsp;\u003c/strong\u003eNone.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003cstrong\u003eEthics statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eEthical approval was not required for the study involving humans in accordance with the local legislation and institutional requirements. Written informed consent to participate in this study was not required from the participants or the participants\u0026rsquo; legal guardians/next of kin in accordance with the national legislation and the institutional requirements.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eHathroubi, S.; Servetas, S. L.; Windham, I.; Merrell, D. S.; Ottemann, K. M., Helicobacter pylori Biofilm Formation and Its Potential Role in Pathogenesis. \u003cem\u003eMicrobiology and Molecular Biology Reviews : MMBR \u003c/em\u003e\u003cstrong\u003e2018,\u003c/strong\u003e \u003cem\u003e82\u003c/em\u003e (2).\u003c/li\u003e\n\u003cli\u003eMorey, P.; Pfannkuch, L.; Pang, E.; Boccellato, F.; Sigal, M.; Imai-Matsushima, A.; Dyer, V.; Koch, M.; Mollenkopf, H.-J.; Schlaermann, P.; Meyer, T. F., Helicobacter pylori Depletes Cholesterol in Gastric Glands to Prevent Interferon Gamma Signaling and Escape the Inflammatory Response. \u003cem\u003eGastroenterology \u003c/em\u003e\u003cstrong\u003e2018,\u003c/strong\u003e \u003cem\u003e154\u003c/em\u003e (5).\u003c/li\u003e\n\u003cli\u003eTsay, F.-W.; Hsu, P.-I., H. pylori infection and extra-gastroduodenal diseases. \u003cem\u003eJournal of Biomedical Science \u003c/em\u003e\u003cstrong\u003e2018,\u003c/strong\u003e \u003cem\u003e25\u003c/em\u003e (1), 65.\u003c/li\u003e\n\u003cli\u003eTshibangu-Kabamba, E.; Yamaoka, Y., Helicobacter pylori infection and antibiotic resistance - from biology to clinical implications. \u003cem\u003eNature Reviews. Gastroenterology \u0026amp; Hepatology \u003c/em\u003e\u003cstrong\u003e2021,\u003c/strong\u003e \u003cem\u003e18\u003c/em\u003e (9), 613-629.\u003c/li\u003e\n\u003cli\u003eWang, F.; Meng, W.; Wang, B.; Qiao, L., Helicobacter pylori-induced gastric inflammation and gastric cancer. \u003cem\u003eCancer Letters \u003c/em\u003e\u003cstrong\u003e2014,\u003c/strong\u003e \u003cem\u003e345\u003c/em\u003e (2), 196-202.\u003c/li\u003e\n\u003cli\u003eYuan, W.; Li, Y.; Yang, K.; Ma, B.; Guan, Q.; Wang, D.; Yang, L., Iron deficiency anemia in Helicobacter pylori infection: meta-analysis of randomized controlled trials. \u003cem\u003eScandinavian Journal of Gastroenterology \u003c/em\u003e\u003cstrong\u003e2010,\u003c/strong\u003e \u003cem\u003e45\u003c/em\u003e (6), 665-676.\u003c/li\u003e\n\u003cli\u003eShah, S. C.; Piazuelo, M. B.; Kuipers, E. J.; Li, D., AGA Clinical Practice Update on the Diagnosis and Management of Atrophic Gastritis: Expert Review. \u003cem\u003eGastroenterology \u003c/em\u003e\u003cstrong\u003e2021,\u003c/strong\u003e \u003cem\u003e161\u003c/em\u003e (4).\u003c/li\u003e\n\u003cli\u003eQu, X.-H.; Huang, X.-L.; Xiong, P.; Zhu, C.-Y.; Huang, Y.-L.; Lu, L.-G.; Sun, X.; Rong, L.; Zhong, L.; Sun, D.-Y.; Lin, H.; Cai, M.-C.; Chen, Z.-W.; Hu, B.; Wu, L.-M.; Jiang, Y.-B.; Yan, W.-L., Does Helicobacter pylori infection play a role in iron deficiency anemia? A meta-analysis. \u003cem\u003eWorld Journal of Gastroenterology \u003c/em\u003e\u003cstrong\u003e2010,\u003c/strong\u003e \u003cem\u003e16\u003c/em\u003e (7), 886-896.\u003c/li\u003e\n\u003cli\u003eTan, H.-J.; Goh, K.-L., Extragastrointestinal manifestations of Helicobacter pylori infection: facts or myth? A critical review. \u003cem\u003eJournal of Digestive Diseases \u003c/em\u003e\u003cstrong\u003e2012,\u003c/strong\u003e \u003cem\u003e13\u003c/em\u003e (7), 342-349.\u003c/li\u003e\n\u003cli\u003eSarari, A. S.; Farraj, M. A.; Hamoudi, W.; Essawi, T. A., Helicobacter pylori, a causative agent of vitamin B12 deficiency. \u003cem\u003eJournal of Infection In Developing Countries \u003c/em\u003e\u003cstrong\u003e2008,\u003c/strong\u003e \u003cem\u003e2\u003c/em\u003e (5), 346-349.\u003c/li\u003e\n\u003cli\u003eHe, J.; Liu, Y.; Ouyang, Q.; Li, R.; Li, J.; Chen, W.; Hu, W.; He, L.; Bao, Q.; Li, P.; Hu, C., Helicobacter pylori and unignorable extragastric diseases: Mechanism and implications. \u003cem\u003eFrontiers In Microbiology \u003c/em\u003e\u003cstrong\u003e2022,\u003c/strong\u003e \u003cem\u003e13\u003c/em\u003e, 972777.\u003c/li\u003e\n\u003cli\u003eSkrivankova, V. W.; Richmond, R. C.; Woolf, B. A. R.; Davies, N. M.; Swanson, S. A.; VanderWeele, T. J.; Timpson, N. J.; Higgins, J. P. T.; Dimou, N.; Langenberg, C.; Loder, E. W.; Golub, R. M.; Egger, M.; Davey Smith, G.; Richards, J. B., Strengthening the reporting of observational studies in epidemiology using mendelian randomisation (STROBE-MR): explanation and elaboration. \u003cem\u003eBMJ (Clinical Research ed.) \u003c/em\u003e\u003cstrong\u003e2021,\u003c/strong\u003e \u003cem\u003e375\u003c/em\u003e, n2233.\u003c/li\u003e\n\u003cli\u003eChen, J.; Zhang, J.; Ma, X.; Ren, Y.; Tang, Y.; Zhang, Z.; Ye, W.; Zhang, X.; Lin, Z.; Wang, L.; Li, Z., Causal relationship between Helicobacter pylori antibodies and gastroesophageal reflux disease (GERD): A mendelian study. \u003cem\u003ePloS One \u003c/em\u003e\u003cstrong\u003e2023,\u003c/strong\u003e \u003cem\u003e18\u003c/em\u003e (12), e0294771.\u003c/li\u003e\n\u003cli\u003eLiu, Y.; Xu, H.; Zhao, Z.; Dong, Y.; Wang, X.; Niu, J., No evidence for a causal link between Helicobacter pylori infection and nonalcoholic fatty liver disease: A bidirectional Mendelian randomization study. \u003cem\u003eFrontiers In Microbiology \u003c/em\u003e\u003cstrong\u003e2022,\u003c/strong\u003e \u003cem\u003e13\u003c/em\u003e, 1018322.\u003c/li\u003e\n\u003cli\u003eGreenland, S., An introduction to instrumental variables for epidemiologists. \u003cem\u003eInt J Epidemiol \u003c/em\u003e\u003cstrong\u003e2000,\u003c/strong\u003e \u003cem\u003e29\u003c/em\u003e (4), 722-9.\u003c/li\u003e\n\u003cli\u003eMayerle, J.; den Hoed, C. M.; Schurmann, C.; Stolk, L.; Homuth, G.; Peters, M. J.; Capelle, L. G.; Zimmermann, K.; Rivadeneira, F.; Gruska, S.; V\u0026ouml;lzke, H.; de Vries, A. C.; V\u0026ouml;lker, U.; Teumer, A.; van Meurs, J. B.; Steinmetz, I.; Nauck, M.; Ernst, F.; Weiss, F. U.; Hofman, A.; Zenker, M.; Kroemer, H. K.; Prokisch, H.; Uitterlinden, A. G.; Lerch, M. M.; Kuipers, E. J., Identification of genetic loci associated with Helicobacter pylori serologic status. \u003cem\u003eJama \u003c/em\u003e\u003cstrong\u003e2013,\u003c/strong\u003e \u003cem\u003e309\u003c/em\u003e (18), 1912-20.\u003c/li\u003e\n\u003cli\u003eButler-Laporte, G.; Kreuzer, D.; Nakanishi, T.; Harroud, A.; Forgetta, V.; Richards, J. B., Genetic Determinants of Antibody-Mediated Immune Responses to Infectious Diseases Agents: A Genome-Wide and HLA Association Study. \u003cem\u003eOpen Forum Infectious Diseases \u003c/em\u003e\u003cstrong\u003e2020,\u003c/strong\u003e \u003cem\u003e7\u003c/em\u003e (11), ofaa450.\u003c/li\u003e\n\u003cli\u003eKurki, M. I.; Karjalainen, J.; Palta, P.; Sipil\u0026auml;, T. P.; Kristiansson, K.; Donner, K. M.; Reeve, M. P.; Laivuori, H.; Aavikko, M.; Kaunisto, M. A.; Loukola, A.; Lahtela, E.; Mattsson, H.; Laiho, P.; Della Briotta Parolo, P.; Lehisto, A. A.; Kanai, M.; Mars, N.; R\u0026auml;m\u0026ouml;, J.; Kiiskinen, T.; Heyne, H. O.; Veerapen, K.; R\u0026uuml;eger, S.; Lemmel\u0026auml;, S.; Zhou, W.; Ruotsalainen, S.; P\u0026auml;rn, K.; Hiekkalinna, T.; Koskelainen, S.; Paajanen, T.; Llorens, V.; Gracia-Tabuenca, J.; Siirtola, H.; Reis, K.; Elnahas, A. G.; Sun, B.; Foley, C. N.; Aalto-Set\u0026auml;l\u0026auml;, K.; Alasoo, K.; Arvas, M.; Auro, K.; Biswas, S.; Bizaki-Vallaskangas, A.; Carpen, O.; Chen, C.-Y.; Dada, O. A.; Ding, Z.; Ehm, M. G.; Eklund, K.; F\u0026auml;rkkil\u0026auml;, M.; Finucane, H.; Ganna, A.; Ghazal, A.; Graham, R. R.; Green, E. M.; Hakanen, A.; Hautalahti, M.; Hedman, \u0026Aring;. K.; Hiltunen, M.; Hinttala, R.; Hovatta, I.; Hu, X.; Huertas-Vazquez, A.; Huilaja, L.; Hunkapiller, J.; Jacob, H.; Jensen, J.-N.; Joensuu, H.; John, S.; Julkunen, V.; Jung, M.; Junttila, J.; Kaarniranta, K.; K\u0026auml;h\u0026ouml;nen, M.; Kajanne, R.; Kallio, L.; K\u0026auml;lvi\u0026auml;inen, R.; Kaprio, J.; Kerimov, N.; Kettunen, J.; Kilpel\u0026auml;inen, E.; Kilpi, T.; Klinger, K.; Kosma, V.-M.; Kuopio, T.; Kurra, V.; Laisk, T.; Laukkanen, J.; Lawless, N.; Liu, A.; Longerich, S.; M\u0026auml;gi, R.; M\u0026auml;kel\u0026auml;, J.; M\u0026auml;kitie, A.; Malarstig, A.; Mannermaa, A.; Maranville, J.; Matakidou, A.; Meretoja, T.; Mozaffari, S. V.; Niemi, M. E. K.; Niemi, M.; Niiranen, T.; O Donnell, C. J.; Obeidat, M. E.; Okafo, G.; Ollila, H. M.; Palom\u0026auml;ki, A.; Palotie, T.; Partanen, J.; Paul, D. S.; Pelkonen, M.; Pendergrass, R. K.; Petrovski, S.; Pitk\u0026auml;ranta, A.; Platt, A.; Pulford, D.; Punkka, E.; Pussinen, P.; Raghavan, N.; Rahimov, F.; Rajpal, D.; Renaud, N. A.; Riley-Gillis, B.; Rodosthenous, R.; Saarentaus, E.; Salminen, A.; Salminen, E.; Salomaa, V.; Schleutker, J.; Serpi, R.; Shen, H.-Y.; Siegel, R.; Silander, K.; Siltanen, S.; Soini, S.; Soininen, H.; Sul, J. H.; Tachmazidou, I.; Tasanen, K.; Tienari, P.; Toppila-Salmi, S.; Tukiainen, T.; Tuomi, T.; Turunen, J. A.; Ulirsch, J. C.; Vaura, F.; Virolainen, P.; Waring, J.; Waterworth, D.; Yang, R.; Nelis, M.; Reigo, A.; Metspalu, A.; Milani, L.; Esko, T.; Fox, C.; Havulinna, A. S.; Perola, M.; Ripatti, S.; Jalanko, A.; Laitinen, T.; M\u0026auml;kel\u0026auml;, T. P.; Plenge, R.; McCarthy, M.; Runz, H.; Daly, M. J.; Palotie, A., FinnGen provides genetic insights from a well-phenotyped isolated population. \u003cem\u003eNature \u003c/em\u003e\u003cstrong\u003e2023,\u003c/strong\u003e \u003cem\u003e613\u003c/em\u003e (7944), 508-518.\u003c/li\u003e\n\u003cli\u003eEyoum Bille, B. B.; Kouitcheu Mabeku, L. B., Relationship between active Helicobacter pylori infection and anemia, iron deficiency, iron deficiency anemia: A cross-sectional study in a sub-Saharan setting. \u003cem\u003eJGH Open : an Open Access Journal of Gastroenterology and Hepatology \u003c/em\u003e\u003cstrong\u003e2022,\u003c/strong\u003e \u003cem\u003e6\u003c/em\u003e (8), 554-568.\u003c/li\u003e\n\u003cli\u003eHudak, L.; Jaraisy, A.; Haj, S.; Muhsen, K., An updated systematic review and meta-analysis on the association between Helicobacter pylori infection and iron deficiency anemia. \u003cem\u003eHelicobacter \u003c/em\u003e\u003cstrong\u003e2017,\u003c/strong\u003e \u003cem\u003e22\u003c/em\u003e (1).\u003c/li\u003e\n\u003cli\u003eUlasoglu, C.; Temiz, H. E.; Sağlam, Z. A., The Relation of Cytotoxin-Associated Gene-A Seropositivity with Vitamin B12 Deficiency in Helicobacter pylori-Positive Patients. \u003cem\u003eBioMed Research International \u003c/em\u003e\u003cstrong\u003e2019,\u003c/strong\u003e \u003cem\u003e2019\u003c/em\u003e, 1450536.\u003c/li\u003e\n\u003cli\u003eG\u0026ouml;kışık, M. T.; Uyar, S., The role of Helicobacter pylori in vitamin-B12 deficiency due to metformin use. \u003cem\u003eHelicobacter \u003c/em\u003e\u003cstrong\u003e2020,\u003c/strong\u003e \u003cem\u003e25\u003c/em\u003e (5), e12718.\u003c/li\u003e\n\u003cli\u003eLee, J. Y.; Kim, S. E.; Park, S. J.; Park, M. I.; Moon, W.; Kim, J. H.; Jung, K., Helicobacter pylori infection and iron deficiency in non-elderly adults participating in a health check-up program. \u003cem\u003eThe Korean Journal of Internal Medicine \u003c/em\u003e\u003cstrong\u003e2022,\u003c/strong\u003e \u003cem\u003e37\u003c/em\u003e (2), 304-312.\u003c/li\u003e\n\u003cli\u003eMendoza, E.; Duque, X.; Hern\u0026aacute;ndez Franco, J. I.; Reyes Maldonado, E.; Mor\u0026aacute;n, S.; Mart\u0026iacute;nez, G.; Salinas Rodr\u0026iacute;guez, A.; Mart\u0026iacute;nez, H., Association between Active H. pylori Infection and Iron Deficiency Assessed by Serum Hepcidin Levels in School-Age Children. \u003cem\u003eNutrients \u003c/em\u003e\u003cstrong\u003e2019,\u003c/strong\u003e \u003cem\u003e11\u003c/em\u003e (9).\u003c/li\u003e\n\u003cli\u003ePinar, I. E.; Mavis, O., The Effect of Helicobacter pylori Density on Serum Vitamin B12 and Folate Levels in Patients With Non-atrophic Gastritis. \u003cem\u003eCureus \u003c/em\u003e\u003cstrong\u003e2023,\u003c/strong\u003e \u003cem\u003e15\u003c/em\u003e (9), e45252.\u003c/li\u003e\n\u003cli\u003eKatelaris, P.; Hunt, R.; Bazzoli, F.; Cohen, H.; Fock, K. M.; Gemilyan, M.; Malfertheiner, P.; M\u0026eacute;graud, F.; Piscoya, A.; Quach, D.; Vakil, N.; Vaz Coelho, L. G.; LeMair, A.; Melberg, J., Helicobacter pylori World Gastroenterology Organization Global Guideline. \u003cem\u003eJournal of Clinical Gastroenterology \u003c/em\u003e\u003cstrong\u003e2023,\u003c/strong\u003e \u003cem\u003e57\u003c/em\u003e (2), 111-126.\u003c/li\u003e\n\u003cli\u003eViazis, N.; Argyriou, K.; Kotzampassi, K.; Christodoulou, D. K.; Apostolopoulos, P.; Georgopoulos, S. D.; Liatsos, C.; Giouleme, O.; Koustenis, K.; Veretanos, C.; Stogiannou, D.; Moutzoukis, M.; Poutakidis, C.; Mylonas, I. I.; Tseti, I.; Mantzaris, G. J., A Four-Probiotics Regimen Combined with A Standard Helicobacter pylori-Eradication Treatment Reduces Side Effects and Increases Eradication Rates. \u003cem\u003eNutrients \u003c/em\u003e\u003cstrong\u003e2022,\u003c/strong\u003e \u003cem\u003e14\u003c/em\u003e (3).\u003c/li\u003e\n\u003cli\u003eChen, W.; Shi, S.; Tu, J.; Liao, L.; Liao, Y.; Chen, K.; Chen, L.; Huang, R., Nutrition-related diseases and cardiovascular mortality in American society: national health and nutrition examination study, 1999-2006. \u003cem\u003eBMC Public Health \u003c/em\u003e\u003cstrong\u003e2022,\u003c/strong\u003e \u003cem\u003e22\u003c/em\u003e (1), 1849.\u003c/li\u003e\n\u003cli\u003eLi, Y.; Choi, H.; Leung, K.; Jiang, F.; Graham, D. Y.; Leung, W. K., Global prevalence of Helicobacter pylori infection between 1980 and 2022: a systematic review and meta-analysis. \u003cem\u003eThe Lancet. Gastroenterology \u0026amp; Hepatology \u003c/em\u003e\u003cstrong\u003e2023,\u003c/strong\u003e \u003cem\u003e8\u003c/em\u003e (6), 553-564.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Helicobacter pylori, anemia, iron deficiency anemia, vitamin B12 deficiency anemia, Mendelian Randomization","lastPublishedDoi":"10.21203/rs.3.rs-3940357/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-3940357/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003eObservational studies have reported a correlation between \u003cem\u003eHelicobacter pylori\u003c/em\u003e infection and an increased incidence of anemia, iron deficiency anemia (IDA), and vitamin B12 deficiency anemia. However, the fundamental cause remains elusive. This study aimed to ascertain the causal relationship between \u003cem\u003eH. pylori\u003c/em\u003e infection and anemia.\u003c/p\u003e\u003ch2\u003eMethod\u003c/h2\u003e \u003cp\u003eUsing data from genome-wide association studies (GWAS), we executed a bidirectional Mendelian randomization (MR) study utilizing two-sample GWAS. The principal analytical method was the inverse variance weighted (IVW) method. We employed a conservative Bonferroni-corrected threshold (p\u0026thinsp;\u0026lt;\u0026thinsp;2.38 \u0026times; 10\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e). Sensitivity analyses were implemented with Cochran\u0026rsquo;s Q test and MR-Egger regression.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eGenetically predicted \u003cem\u003eH. pylori\u003c/em\u003e infection, anti-\u003cem\u003eH. pylori\u003c/em\u003e CagA, VacA, and IgG seropositivity was not causally associated with anemia, IDA, or vitamin B12 deficiency anemia (p\u0026thinsp;\u0026gt;\u0026thinsp;2.38 \u0026times; 10\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e). Furthermore, reverse MR analysis did not reveal evidence for a causal effect of anemia on H. pylori infection (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05).\u003c/p\u003e\u003ch2\u003eConclusions\u003c/h2\u003e \u003cp\u003eUtilizing genetic data, MR analysis demonstrated the absence of evidence for a causal association between the seroprevalence of \u003cem\u003eH. pylori\u003c/em\u003e infection and anemia. Further research is needed to elucidate the relationship between H. pylori infection and anemia.\u003c/p\u003e","manuscriptTitle":"Associations of Helicobacter Pylori with Anemia: A Bidirectional Two-Sample Mendelian Randomization Study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-02-22 07:44:55","doi":"10.21203/rs.3.rs-3940357/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"9f5f3c10-53cc-47a5-b42a-a214c75fd501","owner":[],"postedDate":"February 22nd, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2024-03-25T11:24:04+00:00","versionOfRecord":[],"versionCreatedAt":"2024-02-22 07:44:55","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-3940357","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-3940357","identity":"rs-3940357","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}