Objectives: To clarify the effect of tooth loss on development of all-cause dementia and its subtypes in an elderly Japanese population. Design: Prospective cohort study. Setting: The Hisayama Study, Japan. Participants: Community-dwelling Japanese adults without dementia aged 60 and older (N = 1,566) were followed for 5 years (2007–2012). Measurements: Participants were classified into four categories according to baseline number of remaining teeth (≥20, 10–19, 1–9, 0). The risk estimates of the effect of tooth loss on the development of all-cause dementia, Alzheimer's disease (AD), and vascular dementia (VaD) were computed using a Cox proportional hazards model. Results: During follow-up, 180 (11.5%) subjects developed all-cause dementia; 127 (8.1%) had AD, and 42 (2.7%) had VaD. After adjusting for potential confounders, there was a tendency for the multivariable-adjusted hazard ratio of all-cause dementia to increase with decrease in number of remaining teeth (P for trend =.04). The risk of all-cause dementia was 1.62 times as great in subjects with 10 to 19 teeth, 1.81 times as great in those with one to nine teeth, and 1.63 times as great in those with no teeth as in those with 20 teeth or more. An inverse association was observed between number of remaining teeth and risk of AD (P for trend =.08), but no such association was observed with risk of VaD (P for trend =.20). Conclusion: Tooth loss is associated with an increased risk of all-cause dementia and AD in the Japanese population.
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