Insulin resistance as a mediator between obesity and periodontitis risk.

BACKGROUND: Obesity is a well-established risk factor for periodontitis, a chronic inflammatory disease with systemic implications. While diabetes has been proposed as a potential mediator in this relationship, its clinical heterogeneity limits its utility in causal modeling. Insulin resistance, quantified by the Homeostasis Model Assessment of Insulin Resistance (HOMA-IR), offers a more mechanistically grounded alternative. OBJECTIVES: This study aimed to investigate the associations between obesity, insulin resistance, and periodontitis, with a specific focus on the mediating role of HOMA-IR. METHODS: Data from the National Health and Nutrition Examination Survey (NHANES, 2009-2012) including 8,473 participants were analyzed. Obesity was assessed using body mass index (BMI) and waist circumference (WC), and insulin resistance was measured using HOMA-IR. Periodontitis was evaluated using clinical attachment loss and probing depth. Multivariable logistic regression, restricted cubic splines, and mediation analyses were conducted. RESULTS: Both BMI and WC were significantly associated with an increased risk of periodontitis (P < 0.05). HOMA-IR was positively associated with periodontitis risk (P < 0.01). Mediation analysis revealed that HOMA-IR mediated 63.44% of the association between BMI and periodontitis and 36.77% of that between WC and periodontitis. Nonlinear analyses showed no significant nonlinear trends. CONCLUSIONS: Insulin resistance, as reflected by HOMA-IR, plays a significant mediating role in the relationship between obesity and periodontitis. These findings underscore the importance of early metabolic regulation in mitigating obesity-related periodontal risk and provide mechanistic insight into the interplay between systemic and oral health.