Association between tooth loss and kidney function: indirect roles of oxidative stress and systemic inflammation in NHANES 2001–2020

Tooth loss and chronic kidney disease (CKD) are globally prevalent conditions with substantial impacts on overall health. Previous evidence suggests an association between tooth loss and CKD, but its characteristics and potential biological pathways remain unclear. This study examined the association between tooth loss and estimated glomerular filtration rate (eGFR)-related CKD and explored potential indirect associations of systemic oxidative stress, quantified by the oxidative balance score (OBS), and the systemic immune-inflammation index (SII). We conducted a cross-sectional analysis of participants from the 2001–2020 National Health and Nutrition Examination Survey (NHANES). Regression models were fitted to examine the associations of tooth loss with eGFR, OBS, and SII, together with the associations of OBS and SII with eGFR. In addition, bootstrap analyses were used to estimate potential indirect associations of systemic oxidative stress and SII in the association between tooth loss and eGFR. A total of 17,833 participants were included, with 1,837 in the CKD group (eGFR < 60 mL/min/1.73 m²) and 15,996 in the non-CKD group. In the model after covariate adjustment, tooth loss in the fourth quartile was negatively correlated with eGFR in females (β = -1.291[-2.343, -0.238], P < 0.05) and associated with a higher risk of CKD (OR = 1.379[1.079, 1.763], P < 0.05), but this association was not significant in males. In females, higher tooth loss was associated with lower OBS and higher SII. Mediation analyses estimated potential indirect associations through OBS and SII in the association between tooth loss and eGFR, with estimated proportions of 13.514% and 4.054%, respectively. This study found an association between tooth loss and eGFR-related CKD, particularly in females. Systemic oxidative stress (calculated by OBS) and SII showed potential indirect associations in females, providing insight into possible systemic pathways linking tooth loss and renal function. These findings support further longitudinal investigation of oxidative and inflammatory pathways underlying the relationship between oral health and kidney function. Tooth loss has been associated with CKD, but sex-specific patterns and potential systemic pathways remain unclear. In this large NHANES analysis, greater tooth loss was associated with lower eGFR and higher odds of CKD, particularly among females. Among females, greater tooth loss was associated with lower OBS and higher SII, both of which showed indirect statistical associations with eGFR. These indirect associations should be interpreted as exploratory rather than causal because of the cross-sectional design. Tooth loss observed during routine dental examinations may help identify medically vulnerable individuals who could benefit from risk-based medical evaluation, although it is not a stand-alone CKD screening tool.