Poor periodontal health linked to higher dementia

Dental Tribune International

Wed. 7. October 2026

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FUKUOKA, Japan: Poor oral health has increasingly been investigated in relation to dementia, but longitudinal studies specifically on periodontitis have had mixed findings. Researchers in Japan have now used longitudinal data to investigate periodontal health in relation to subsequent dementia. By incorporating repeated periodontal assessments and examining dementia subtypes separately, the study addresses gaps in earlier research and provides more detailed evidence on the association.

Because cognitive changes can begin years before dementia is diagnosed and may themselves lead to poorer oral health, long-term follow-up is important for addressing the possibility of reverse causality. The researchers therefore analysed data from the Hisayama Study, an ongoing population-based prospective cohort study. The analysis followed 1,396 adults aged 60 and over without dementia at baseline for up for ten years.

During follow-up, about one in five participants developed dementia. Most of these cases involved Alzheimer’s disease, and some involved vascular dementia, a form of dementia caused by impaired blood flow to the brain. Greater average periodontal pocket depth, attachment loss and bleeding on probing at baseline were each associated with a higher risk of dementia after the researchers took account of demographic, health and lifestyle factors that may have contributed to dementia risk. Greater bleeding on probing was associated with Alzheimer’s disease. The findings for vascular dementia, however, were inconsistent.

A notable feature of the study was that periodontal status was reassessed after five years. When the researchers incorporated the updated periodontal measurements, greater pocket depth, attachment loss and bleeding on probing remained associated with dementia overall. All three measures were also associated with Alzheimer’s disease in the updated analyses, but none with vascular dementia.

The researchers also investigated whether early cognitive deterioration could have contributed to poorer periodontal health before dementia was diagnosed. They repeated the analysis excluding dementia cases diagnosed during the first two years and then all cases diagnosed during the first three years. The overall pattern remained similar in the two-year analysis. In the three-year analysis, some associations were weaker, but bleeding on probing remained associated with dementia overall and with Alzheimer’s disease.

The authors proposed that chronic periodontal inflammation may contribute to systemic inflammation and subsequently to vascular changes affecting the brain. However, a recent review argued that reverse causality remains an important challenge when interpreting links between oral health and dementia, and it suggested that difficulties with eating and speaking may reduce social interaction and contribute to social isolation, itself a recognised modifiable risk factor for dementia.

The findings add to earlier longitudinal evidence linking poor periodontal health and tooth loss with cognitive decline and dementia. A systematic review and meta-analysis published in September subsequently reported modest associations between periodontitis and tooth loss with dementia and mild cognitive impairment.

The study, titled “Periodontal status and the risk of all-cause dementia, Alzheimer’s disease and vascular dementia in a community: The Hisayama Study”, was published on 16 August 2026 in the Journal of Clinical Periodontology, ahead of final publication.

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Dementia Dental research Geriatric dentistry Japan Mental health Periodontal disease

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