Nutrition Status Plays a Partial Mediation Role in the Relationship between Number of Teeth and Frailty: A Cross-Sectional Multicenter Study

Introduction: Although the relationship between the number of teeth and frailty has been extensively studied, the mediating role of nutrition status in the association between the number of teeth and frailty remains to be clarified. Methods: A number of 6,664 participants lived in the communities of West China were analyzed in our study. Physical frailty was determined based on the phenotype established by Fried. Nutrition status was evaluated using the Mini Nutrition Assessment-Short Form (MNA-SF) scale. Multiple linear regression was employed to evaluate the direct relationships between the number of teeth, nutrition, and frailty. Mediation models and structural equation model (SEM) pathway analysis were used to test the mediating role of nutrition status in the relationship between the number of teeth and frailty. Results: Among the 6,664 participants aged over 50 years old, the prevalence of frailty was 6.2%. Multiple linear regression analysis showed a significant total relationship between the number of teeth (β = −0.359, 95% CI: −0.473 to −0.244, p < 0.001) and frailty. After adjusting for MNA-SF scores, the relationship between the number of teeth and frailty remained significant (β = −0.327, 95% CI: −0.443 to −0.211, p < 0.001), indicating a partial mediating effect of nutrition. Mediation analysis verified that nutrition partially mediated the relationship between the number of teeth and frailty (indirect effect estimate = −0.0121, bootstrap 95% CI: −0.0151 to −0.0092; direct effect estimate = −0.0874, bootstrap 95% CI: −0.1086 to −0.0678) in the fully adjusted model. This mediating effect occurred through influencing weight loss, low level of physical activity, and debility. SEM framework pathway analysis confirmed the association between the number of teeth, nutrition, and frailty. Conclusions: Our findings demonstrated that frailty was correlated with the number of teeth and poorer nutritional status, with nutrition partially mediating the correlation between the number of teeth and frailty. Our results supported early nutritional evaluation and intervention in oral health to decrease the risk of frailty.