Community-Level Inequalities and Risk Factors for Incident Oral Frailty

Oral frailty, characterized by tooth loss, chewing difficulty, and swallowing problems, has been associated with adverse health outcomes in older adults. However, longitudinal evidence on community-level inequalities and determinants of incident oral frailty remains limited.

This cohort study aimed to examine community-level inequalities in the incidence of oral frailty and identify individual- and municipality-level factors associated with its onset among older adults in Japan.

We analyzed data from 42,987 participants aged ≥65 y who completed the Japan Gerontological Evaluation Study surveys in 2019 and 2022. Oral frailty was determined using a validated prediction model including age, number of teeth, chewing difficulty, and choking. Individual-level variables included sociodemographic, health status, and social capital indicators. Municipality-level variables included population density, aggregated social capital, and the presence of prefectural or municipal dental health ordinances. Modified multilevel Poisson regression was used to estimate incidence rate ratios.

The incidence of oral frailty varied across municipalities, ranging from 17.1% to 33.3%. In the fully adjusted multilevel model, individual-level factors significantly associated with a higher risk of incident oral frailty were male sex; being widowed, divorced, or never married; lower educational attainment; lower equivalent income; smoking history; current illness; and lack of social cohesion (P < 0.05). At the municipality level, residing in urban, semi-urban, or rural-agricultural areas was associated with a lower risk of incident oral frailty compared with metropolitan area residency. Although not statistically significant in all models, higher municipality-level civic participation tended to be associated with a lower risk of incident oral frailty.

Community-level inequalities in the incidence of oral frailty are driven by both individual vulnerabilities and municipality-level factors. Notably, higher municipality-level civic participation tended to be associated with a lower incidence of oral frailty. Effective prevention requires comprehensive strategies that address socioeconomic factors and promote community-level civic participation.Knowledge Transfer Statement:This nationwide cohort study demonstrates that community-level inequalities in the incidence of oral frailty are substantial. They are largely explained not only by modifiable individual socioeconomic factors but also by municipality-level civic participation. These findings highlight the importance of integrating individual risk-based prevention with community strategies that may contribute to reducing oral frailty and related oral health disparities in aging populations.