Tooth Loss and Risk of Dementia in the Community: the Hisayama Study

Abstract

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)(2008)(2009)(2010)(2011)(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 multivariableadjusted 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. J Am Geriatr Soc 65:e95-e100, 2017.Key words: Alzheimer's disease; epidemiology; oral health; prospective cohort study; vascular dementia T he increase in the incidence of dementia is a substantial public health concern in aging societies. Approximately 46.8 million people worldwide have dementia, and the incidence is 9.9 million per year.1 The number of people living with dementia will nearly double every 20 years, but the causes of dementia, especially Alzheimer's disease (AD), are unclear, and there is a lack of treatments and health service settings for this disorder.2,3 Therefore, intensified research studies are needed to identify factors that have the potential to decrease the risk of dementia and thereby decrease the burden of this disease on health systems.A growing number of research studies have focused on the link between oral health and cognitive status. In particular, many research studies have assessed the association between number of teeth and cognitive function, [4][5][6][7][8][9][10][11][12][13][14][15] but the results of observational longitudinal studies on the effect of tooth loss on cognitive function are inconsistent. A recent systematic review of the literature suggested that tooth loss was associated with greater risk of cognitive impairment and dementia, 16 whereas another reported that tooth loss was not consistently associated with those outcomes. 17 The inconsistency might be due to methodological deficiencies in this field, such as the lack of representativeness of the ...

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