Association Between Periodontal Disease and Cognitive Impairment: A Systematic Review and Meta-Analysis

Background: Cognitive impairment is an increasing global health burden, and growing evidence suggests that periodontitis may contribute to cognitive decline through chronic inflammation and other oral-systemic pathways. This systematic review aimed to evaluate the association between periodontal disease and cognitive impairment in adults and to contextualize the findings within prior evidence syntheses. In this review, periodontitis is conceptualized as a host-mediated chronic inflammatory burden rather than as a marker of intraoral infection alone. Methods: A PRISMA-based systematic review was conducted using PubMed, Web of Science, and Scopus for observational studies published between 2015 and December 2025. Eligible studies included adults assessed for both periodontal status and cognition using validated clinical, radiographic, and neuropsychological measures. Risk of bias was assessed with the Newcastle-Ottawa Scale, and the certainty of the evidence was judged qualitatively. Database-specific search strategies are provided. Results: Nine studies met the inclusion criteria, including prospective cohort, cross-sectional, and Alzheimer disease cohorts. Across studies, more severe periodontitis was consistently associated with poorer cognitive performance, higher odds of mild cognitive impairment, and faster cognitive decline. In the four studies eligible for quantitative synthesis, the random-effects estimate indicated an approximately twofold overall association estimate (2.12; 95% CI 1.51-2.98), which is best interpreted as a summary association measure rather than a precise risk estimate. In Alzheimer disease cohorts, periodontal inflammation was associated with accelerated deterioration, including a six-fold greater rate of cognitive decline in one study and faster worsening on standardized cognitive scales in another. Risk-of-bias assessment showed three studies at low risk and six at moderate risk, with no study judged high risk. However, the overall certainty of the evidence was considered low because the evidence base was observational, clinically heterogeneous, and vulnerable to residual confounding and possible publication bias; this judgment reflects a qualitative interpretation of the included study designs and their methodological limitations rather than a formal GRADE rating. Conclusions: The current evidence supports a consistent, approximately twofold overall association between periodontal disease and cognitive impairment, broadly in line with prior systematic reviews and meta-analyses, while adding newer cohort and Alzheimer disease data through 2025. The exposure is best understood as a host-mediated periodontal inflammatory burden, and Periodontitis may represent a potentially modifiable contributor to adverse cognitive outcomes, but causal inference and policy-level screening recommendations require stronger interventional and mechanistic evidence. Clinical Relevance: Periodontitis represents a potentially modifiable risk factor for cognitive decline and accelerated deterioration in Alzheimer's disease patients, highlighting the need for interdisciplinary collaboration between dental and medical professionals. Integrating routine periodontal screenings and proactive oral care into the management of aging populations could serve as a valuable, low-risk strategy to help mitigate adverse cognitive outcomes.