Helicobacter pylori infection and risk for developing dementia: an evidence-based meta-analysis of case-control and cohort studies

Background: Infection with multiple pathogens may play a key role in the pathogenesis of dementia. Whether Helicobacter pylori (H. pylori) infection is associated causally with dementia is controversial. Objective: We conduct a meta-analysis of case-control and cohort studies on the association between H. pylori infection and the risk for all-cause and Alzheimer’s disease (AD) dementia. Methods: Two independent reviewers searched the PubMed, Cochrane Library, and Embase databases with English language restrictions from the date of conception to September 18, 2020. The primary analysis was as follows: the exposure variable was H. pylori infection, and the outcome was incident all-cause and AD dementia. Pooled odds ratios (OR), relative risk (RR), and corresponding 95% confidence intervals (CI) were obtained using the fixed-or random-effect model. Forest plots were generated to summarize the results. Results: Ten studies involving 96,561 participants were included in the meta-analysis: 5 case-control studies and 5 cohort studies. The overall pooled cohort studies showed a significant positive association between H. pylori infection and all-cause dementia with pooled RR of 1.36 (95% CI, 1.11-1.67). There was no association between H. pylori infection and risk for developing AD: RR of 1.33 (95% CI, 0.86-2.05) in cohort studies, and OR of 1.72 (95% CI, 0.97-3.04) in case-control studies. Significant heterogeneity was showed in each comparison group. Conclusion: This meta-analysis supports a positive association between H. pylori infection and the risk of all-cause dementia, but not AD dementia. Due to the interference of confounding factors, randomized controlled trials are needed to prove their causality.