- Design
- Prospective population-based cohort, 9-year follow-up
- Population
- 47,293 independent adults aged 65 and over, Japan
- Primary outcome
- Incident dementia
- Effect
- No teeth vs ≥20: HR 1.27 (1.18–1.36); PAF 7.2%
This prospective cohort followed 47,293 functionally independent adults aged 65 and over in 22 Japanese municipalities from 2013 to 2022. Investigators compared the population attributable fraction of tooth loss with the 12 modifiable risk factors named by the 2024 Lancet Commission on dementia.
During a median nine years, 17.4% developed dementia. Compared with having 20 or more teeth, having none was associated with a hazard ratio of 1.27 (95% CI 1.18–1.36), with smaller increases for 1–19 teeth. Tooth loss accounted for an estimated 7.2% of dementia cases, ranking third after depressive symptoms (10.5%) and social isolation (9.4%); in men it ranked first (12.0%).
The link may run through nutrition, inflammation, social withdrawal or shared disadvantage, and the study cannot separate them. Still, oral health is cheap to ask about, and loss of teeth is visible. In India, where dental care for older adults is often neglected and costly, asking about chewing and dentures belongs in a comprehensive geriatric assessment.
- Ask older patients about chewing difficulty, missing teeth and denture fit
- Refer for dental care as part of a dementia risk-reduction conversation
- Look for weight loss and poor diet in people with few teeth
- Address depression, isolation and hearing alongside oral health
Why it matters
Puts oral health on the same list as hearing, depression and isolation for dementia prevention.
Don't overread it
This observational cohort cannot show that dental treatment prevents dementia.
The statistics, in plain English
A population attributable fraction of 7.2% estimates the share of dementia cases that would not occur if tooth loss had no effect — assuming the association is causal, which this design cannot prove. The hazard ratio of 1.27 is a modest individual-level increase, made important by how common tooth loss is.
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