Oral health is a relevant component for overall health. Oral disease onset at an early age and may harm several health dimensions, especially among older people, and has been associated with frailty.

To evaluate associations between the Frailty Index (FI) and self-reported oral diseases among older, community-dwelling Japanese people.

Cross-sectional and prospective analyses were performed.

We analyzed data from 2,529 participants at the baseline and four-year follow-up of the Nihon University Japanese Longitudinal Study of Aging, which had a four-year follow-up.

We used the self-reported number of teeth, self-reported satisfaction with dentures, and self-reported ability to chew hard food as independent variables. We computed an FI that included 40 deficits as the dependent variable. The FI score ranged from 0 to 1, with a higher score associated with adverse health outcomes and mortality. Considering a gamma distribution and controlling for age, gender, marital status, education, working status, and residence area, we fitted generalized linear models.

We found that dissatisfied denture users had a 2.1% (95% CI 1.006–3.279) higher frailty score than non-denture users at the baseline and a 2.1% (95% CI 0.629–3.690) higher frailty score than non-denture users at the four-year follow-up. In the cross-sectional analysis, with each additional reported tooth at the baseline, the FI score was lower by 1.5% (95% CI −2.878 to −0.208) at the four-year follow-up. In both the cross-sectional and the prospective analyses, the FI scores increased as the ability to chew hard food decreased.

Self-reported oral diseases are associated with the FI score cross-sectionally and prospectively. Identifying factors prospectively associated with frailty may improve strategies for the next generation of older people. Considering oral diseases may help clinicians personalize treatment plans for older people.