Mediating Effect of Protein Intake on the Association Between Number of Remaining Teeth and Functional Decline

To examine whether protein intake mediates the association between the number of remaining teeth and functional decline in older Japanese adults.

Tooth loss has been associated with reduced protein intake and functional decline in older adults. However, whether protein intake mediates this association remains unclear.

We conducted a 6-year longitudinal study using data from a cohort of community-dwelling older adults. Participants aged ≥ 65 years were included. Exposure was the number of teeth (≥ 20, 10-19, and 0-9). The primary outcome was either functional decline or death, and the secondary outcome was weight change. Protein intake was measured using a diet history questionnaire. We used mediation analysis to examine the direct and indirect effects of the number of remaining teeth via protein intake on the outcomes.

Among 1400 eligible participants, the mean ages were 76.3, 76.6, and 78.9 years for groups with ≥ 20, 10-19, and 0-9 teeth, respectively. Protein intake did not mediate the association between the number of teeth and functional decline. In contrast, protein intake showed an indirect association between the number of remaining teeth and weight loss, particularly in individuals with 10-19 teeth than those with ≥ 20 teeth (indirect effect: -0.09% [-0.20, -0.01]).

Although protein intake did not mediate the association between the number of remaining teeth and functional decline, it mediated the association between the number of remaining teeth and weight loss. Interventions targeting oral health and protein intake may prevent weight loss in older adults.