Association Between Reduced Posterior Occlusal Contact and Alzheimer's Disease Onset in Older Japanese Adults: Results from the LIFE Study

Background: An association between poor oral health and cognitive decline has been reported. Most of these studies have considered the number of teeth as a criterion, only a few studies have analyzed the relationship between occlusal status and Alzheimer's disease (AD). Objective: To elucidate whether posterior occlusal contact is associated with AD, focusing on the Eichner classification, among an older population aged 65 years or older in Japan. Methods: This study used monthly claims data of National Health Insurance in Japan from April 2017 to March 2020. The outcome was newly diagnosed AD defined according to ICD-10 code G30. The number of teeth was estimated by dental code data, and occlusal contact was divided into three categories, namely A, B, and C, according to the Eichner classification. Multivariate Cox proportional hazards models were used to analyze the association between a new diagnosis of AD and the Eichner classification. Results: A total of 22,687 participants were included, 560 of whom had newly diagnosed AD during a mean follow-up period of 12.2 months. The AD participants had a lower proportion of Eichner A and a higher proportion of Eichner C. After adjusting for covariates, hazard ratios (95% confidence intervals) with Eichner B and C were 1.34 (1.01-1.77) and 1.54 (1.03-2.30), respectively. Conclusions: In older people aged >= 65 years old, reduced posterior occlusal contact as well as tooth loss have an impact on AD. This study emphasizes the importance of paying attention to occlusal contacts to reduce the risk of AD.