Tooth loss and long-term dementia risk: A nationwide population-based cohort study in the Republic of Korea.

Objective: Evidence linking tooth loss to dementia is limited by cross-sectional designs and short follow-ups. This study examined the association between tooth loss and long-term dementia incidence in a nationwide cohort in the Republic of Korea, from a dental public health perspective. Basic research design: Observational cohort study. Participants: Data from 112,070 adults aged ≥40 years in the National Health Insurance Service-Health Screening Cohort who completed general and oral health examinations in 2005-2006 and were followed for up to 15 years. Main outcome measures: Tooth loss was categorized as 0, 1-7, 8-14, or ≥15 missing teeth. Incident all-cause dementia, Alzheimer's disease, and vascular dementia were identified using diagnostic codes. Cox models estimated adjusted hazard ratios (aHRs) with sensitivity analyses requiring ≥2 diagnoses and subgroup analyses by sex and age. Results: Over a mean 13.5-year follow-up, 7616 participants (6.8%) developed dementia, with higher cumulative incidence observed across increasing levels of tooth loss. Higher aHRs were observed with increasing levels of tooth loss; participants with ≥15 missing teeth had the highest estimates (1 diagnosis: aHR 3.23, 95% CI 2.85-3.64; ≥2 diagnoses: aHR 2.01, 95% CI 1.77-2.28). Associations were similar for Alzheimer's disease and weaker for vascular dementia. Conclusion: Tooth loss was associated with higher long-term dementia risk, supporting its role as a potential population-level oral health indicator relevant to dental public health surveillance and prevention strategies.