Research ReportTooth loss is associated with mild memory impairment in the elderly: The Fujiwara-kyo study
Research Highlights
►Approximately 40% of the subjects with MMI had 0–10 remaining teeth. ►The odds ratio for MMI was 1.71 (95% CI 1.05–2.78) (0–10/ 22–32 remaining teeth). ►These findings suggest that tooth loss is associated with MMI.
Introduction
Several studies have reported that tooth loss is associated with Alzheimer's disease (AD) and dementia (Gatz et al., 2006, Stein et al., 2007). The biological bases are as mentioned below. First, it has been hypothesized (Kamer et al., 2008) that periodontal disease-derived inflammatory molecules, bacteria, and bacterial products enhance brain inflammation (Blasko and Grubeck-Loebenstein, 2003, Rogers, 2008). Tooth loss is an indicator of periodontal disease (Desvarieux et al., 2003, Humphrey et al., 2008). Second, tooth loss may induce nutritional deficits (Kim et al., 2007) and deprivation of sensory information input during mastication (Kondo et al., 1994).
It has been reported that, among persons with mild memory impairment (MMI), 21.2% progress to illnesses with dementia, including AD (10.6%), vascular dementia (4.8%), or other types of dementia (5.8%), over a period of 5 years (Ishikawa and Ikeda, 2007). These individuals represent a high-risk population for dementia. MMI was defined as (Ishikawa et al., 2006): (1) no impairment of the activities of daily living (ADL); (2) normal general cognitive function, as determined using the Mini-Mental State Examination (MMSE) ≥ 24 (Folstein et al., 1975); (3) objective memory impairment, assessed by the three-word delayed recall (Recall) test (score:1 or 0) in the MMSE; (4) absence of dementia or depression, diagnosed by geriatric neuropsychiatrists according to the Diagnostic and Statistical Manual of Mental Disorders, 3rd edn., revised (DSM-Ш R) criteria (American Psychiatric Association, 1987). We hypothesized that tooth loss may also be associated with a preclinical stage of AD and dementia. To our knowledge, few studies have examined this subject. To investigate our hypothesis in a community-based survey, subjects with MMI and elderly controls were identified operationally using the MMSE and Geriatric Depression Scale short version (GDS) (Schreiner et al., 2003). The subjects were also examined for their dental characteristics, serum albumin level, body mass index, medical history, higher-level functional capacity, drinking and smoking habits, frequency of going out, and their performance on a 10-m walking test.
The purpose of this cross-sectional study was twofold: 1) to compare the number of remaining teeth of MMI subjects with those of elderly controls, and 2) to determine whether the relationship between the number of remaining teeth and MMI was modulated by other explanatory variables.
Section snippets
Results
Among the 3,061 subjects available for analysis, MMI was found in 4.5% (69/1,544) of male subjects and 2.1% (32/1,517), a significantly lower percentage, of female subjects. The demographic characteristics of the control and MMI groups are presented in Table 1. Significant differences were found between the two groups for the median age; 71.0 (interquartile range, 7.0) years in the control group vs. 74.0 (9.0) years in the MMI group, length of education, MMSE-total, and the number of remaining
Discussion
The prevalence of MMI examined in our study was 3.0% (MMI, n = 101; participants in baseline examination, n = 3,389). The reported prevalence of community-based mild cognitive impairment (MCI), diagnosed on the criteria of Petersen et al. (1999), after several standardized memory examinations, was 4.9% according to the Tajiri Project in Japan (Meguro et al., 2004), and 2.9–4.0% according to the Monongahela Valley Independent Elders Survey (Ganguli et al., 2004). The prevalence of MMI in this study
Subjects
We used data from the baseline examination of the Fujiwara-kyo study, which was a 5-year prospective cohort study on successful aging in the elderly, conducted on volunteer men and women aged 65 years or older who were living in their homes in Nara prefecture (where the first capital of Japan, called “Fujiwara-kyo”, was established), Japan. A total of 3,389 persons gave their consent for participation in the Fujiwara-kyo study and completed the baseline examination in 2007. Among the 3,389
Acknowledgments
The authors express their sincere gratitude to all participants for their cooperation in this study, the Nara Mannen Seinen Club Association, Yamatokoriyama Koyu Club Association, Kashihara Senior Citizens Club Association, Nara Public Health Center, Koriyama Public Health Center, Nara Dental Association, Kashihara Neighborhood Community Association board members and welfare commissioners, and the Welfare Policy Division of Kashihara City Government. This work was supported by a research grant
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