The Role of Periodontitis in the Initiation and Progression of Cognitive Disorders: An Umbrella Review

Background Cognitive disorders are a major cause of morbidity worldwide, and accumulating evidence indicates that chronic systemic inflammation may play a key role in their initiation and progression. Periodontitis, a prevalent chronic inflammatory oral disease, has been increasingly recognized as a potential risk factor for cognitive disorders. Objective This umbrella review synthesized evidence from systematic reviews and meta-analyses investigating the association between periodontitis and cognitive disorders, including Alzheimer's disease (AD), dementia and cognitive impairment. Methods Following JBI methodological guidance for umbrella reviews, a comprehensive search was conducted across seven databases (Medline, Embase, Cochrane Library, CINAHL, PsycINFO, Web of Science, Scopus) from inception to April 2025 to identify systematic reviews and meta-analyses on the association between periodontitis and cognitive disorders in humans. Two reviewers independently performed study selection, data extraction, and quality appraisal using the JBI Critical Appraisal Tool. Due to heterogeneity, findings were synthesized narratively. Results Twenty systematic reviews and meta-analyses comprising 333 primary studies were included. Most reviews reported a significant association between periodontitis and AD or dementia. Meta-analyses consistently found increased risk estimates, with the strongest associations for severe periodontitis. Biological plausibility was supported by shared inflammatory pathways and detection of periodontal pathogens in brain tissue. However, evidence was predominantly observational, with substantial heterogeneity in diagnostic criteria. Conclusion Evidence suggests a potential link between periodontitis and cognitive disorders, though results are inconsistent and causality remains unproven. Inflammatory and microbial mechanisms are proposed, but well-designed longitudinal and interventional studies with standardized criteria are needed.