Oral health and the risk of dementia: a systematic review, meta-analysis, and comparative evaluation against established systemic risk factors

Oral health has been increasingly associated with dementia and cognitive decline, but the magnitude and consistency of associations across distinct oral-health domains remain unclear. We systematically evaluated domain-specific associations between oral health conditions and dementia-related outcomes and descriptively contextualized their magnitude against selected systemic conditions associated with dementia. PubMed, Scopus, and Web of Science were searched for observational studies published from January 2015 through July 2026. Eligible oral-health exposures were classified into four prespecified domains: tooth loss/dentition, periodontal disease, oral hygiene and dental-care behaviors/utilization, and masticatory function. Cohort-independent estimates were synthesized using random-effects models with restricted maximum likelihood. Sensitivity, subgroup, and exploratory meta-regression analyses were performed, and certainty of evidence was assessed using GRADE. Associations with selected systemic conditions were evaluated descriptively for contextual comparison. Twenty-eight studies were included in the systematic review, and 24 independent study estimates contributed to the primary quantitative synthesis. Poorer tooth loss/dentition status was associated with a pooled relative association of 1.25 (95% CI, 1.15–1.35; k = 6), periodontal disease with 1.30 (95% CI, 1.10–1.54; k = 8), and poorer oral hygiene and dental-care behaviors/utilization with 1.32 (95% CI, 1.21–1.43; k = 7). Masticatory dysfunction showed a larger but imprecise estimate of 1.58 (95% CI, 0.93–2.68; k = 3). Heterogeneity was substantial across domains. Sensitivity analyses generally preserved the direction of the primary findings. The oral-health estimates were within the range reported for several systemic conditions associated with dementia, although these comparisons were descriptive and not head-to-head. Certainty of evidence was low for tooth loss/dentition and very low for the other domains. Poorer oral health was associated with higher dementia-related risk across several distinct domains, with the most precise evidence observed for tooth loss/dentition, periodontal disease, and oral hygiene and dental-care behaviors/utilization. However, substantial heterogeneity and low to very low certainty of evidence preclude causal interpretation. Further well-designed longitudinal studies incorporating relevant life-course factors, and interventional studies where feasible, are needed to clarify the direction and nature of these associations.