Studies have shown that people with cognitive impairment have poor dental health. However, the direction of causality remains unknown. This prospective cohort study aimed to determine the association between four self-reported dental health variables and dementia onset in older Japanese people.
Analysis was conducted on 4425 residents 65 years or older. Four self-reported dental health variables included the number of teeth and/or use of dentures, ability to chew, presence/absence of a regular dentist, and taking care of dental health. Data were collected using self-administered questionnaires given in 2003. Records of dementia onset during 2003 to 2007 were obtained from municipalities in charge of the public long-term care insurance system. Age, income, body mass index, present illness, alcohol consumption, exercise, and forgetfulness were used as covariates.
Dementia onset was recorded in 220 participants. Univariate Cox proportional hazards models showed significant associations between the dental health variables and dementia onset. In models fully adjusted for all covariates, hazard ratios (95% confidence intervals) of dementia onset of respondents were as follows: 1.85 (1.04–3.31) for those with few teeth and without dentures; 1.25 (0.81–1.93) for those who could not chew very well; 1.44 (1.04–2.01) for those who did not have a regular dentist; and 1.76 (0.96–3.20) for those who did not take care of their dental health.
Few teeth without dentures and absence of a regular dentist, not poor mastication and poor attitudes toward dental health, were associated with higher risk of dementia onset in the older Japanese cohort even after adjustment for available covariates.
AGES = Aichi Gerontological Evaluation Study; BMI = body mass index; HR = hazard ratio; CI = confidence interval
From the Division of Sociological Approach in Dentistry (T.Y., Y.H.), Department of Dental Sociology, Kanagawa Dental College, Yokosuka; Center for Well-being and Society (K.K., H.H.), Nihon Fukushi University; Department of Registered Dietitians (M.N.), Faculty of Human Wellness, Tokaigakuen University, Nagoya; Department of International and Community Oral Health (J.A.), Tohoku University Graduate School of Dentistry, Sendai, Japan; and Department of Epidemiology and Public Health (J.A.), University College London, London, United Kingdom.
Address correspondence and reprint requests to Yukio Hirata, DDS, PhD, Division of Sociological Approach in Dentistry, Department of Dental Sociology, Kanagawa Dental College, 82 Inaoka-cho, Yokosuka, Kanagawa 238-8580, Japan. E-mail: firstname.lastname@example.org
This study was not supported by the National Institutes of Health, Wellcome Trust, Howard Hughes Medical Institute, or others. This study was supported in part by a grant of Strategic Research Foundation Grant-aided Project for Private Universities from Ministry of Education, Culture, Sport, Science, and Technology, Japan, 2009 to 2013; and Health Labour Sciences Research Grant, Comprehensive Research on Aging and Health (H22-Choju-Shitei-008) from the Japanese Ministry of Health, Labour and Welfare.
The present study used data from the Aichi Gerontological Evaluation Study. The survey was conducted by the Nihon Fukushi University Center for Well-being and Society as one of their research projects.
The authors have no conflicts of interest to declare.
Received for publication February 24, 2011; revision received October 24, 2011.