Association of a lesser number of teeth with more risk of developing depressive symptoms among middle-aged and older adults in Japan: A 20-year population-based cohort study

[[abstract]]Objectives: This 20-year prospective cohort study aimed to longitudinally explore the relationship between the number of teeth and the incidence of depressive symptoms among community-dwelling middle-aged and older adults. Methods: Data were collected from the National Institute for Longevity Sciences-Longitudinal Study of Aging (NILS-LSA) database from 2002 to 2022 (3rd–9th waves). Data of adults aged ≥40 years were analyzed and those who had depressive symptoms at baseline (3rd wave), had missing data, or did not participate in follow-up, were excluded. We collected data on the number of teeth at baseline. Depressive symptoms were defined as a score of ≥16 on the Center for Epidemiologic Studies Depression Scale. The generalized estimating equation (GEE) model was used to examine the longitudinal relationships between the number of teeth at baseline and the subsequent incidence of depressive symptoms. Results: The final analysis included 1668 participants, with a mean (standard deviation) age of 58.8 (11.1) years and a mean follow-up time of 12.9 years. After GEE analysis with adjustment for multiple covariates, compared to participants with ≥20 teeth, participants with 10–19 teeth and < 10 teeth at baseline were associated with a higher risk of depressive symptoms. The subgroup analysis showed that the effect was stronger in men than in women. Conclusions: Among middle-aged and older community dwellers, particularly men, a small number of teeth after the age of 40 was associated with the future incidence of depressive symptoms