Background <p>Tooth looseness is a clinically relevant self-reported oral health outcome that may reflect compromised tooth support. Sleep disorders have been associated with adverse oral health, but whether metabolic dysfunction contributes to the association between sleep disorder status and tooth looseness remains unclear. This study examined the association between self-reported sleep disorder status and tooth looseness and evaluated whether metabolic dysfunction, reflected by continuous metabolic score for insulin resistance (METS-IR), statistically accounted for part of this association.</p> Materials and methods <p>This study was a secondary data analysis of pooled data from the National Health and Nutrition Examination Survey (NHANES) 2011–2020. Tooth looseness without injury was the outcome, self-reported physician-diagnosed sleep disorder status was the exposure, and continuous METS-IR was specified as the primary intermediate metabolic variable. Elevated METS-IR, defined as METS-IR ≥ 45, was retained for sensitivity analyses. Survey weights and complex design variables were applied. Survey-weighted logistic regression was used to examine the association between sleep disorder status and tooth looseness and the association between continuous METS-IR and tooth looseness. Survey-weighted linear regression was used to examine the association between sleep disorder status and continuous METS-IR. Model 1 was unadjusted. Model 2, the primary adjusted model, adjusted for age, sex, race and ethnicity, education level, poverty-to-income ratio, and ever-smoking status. Model 3 was further adjusted for body mass index as a conservative sensitivity analysis. A regression-based indirect pathway framework was used to evaluate the model-based indirect pathway through continuous METS-IR.</p> Results <p>A total of 4112 participants were included in the final analytic sample, of whom 711 reported tooth looseness without injury. In the primary adjusted model, sleep disorder status was associated with higher odds of tooth looseness (OR = 1.46, 95% CI: 1.04–2.06, <i>p</i> = 0.038). Sleep disorder status was also associated with higher continuous METS-IR levels (<i>β</i> = 9.07, 95% CI: 7.30–10.85, <i>p</i> &lt; 0.001), and continuous METS-IR was associated with tooth looseness (OR = 1.01 per 1-unit increase, 95% CI: 1.01–1.02, <i>p</i> &lt; 0.001). After additional adjustment for BMI, the associations involving METS-IR were attenuated. In the model-based indirect pathway analysis, continuous METS-IR accounted for 23.72% of the total association between sleep disorder status and tooth looseness. Given the secondary analysis of cross-sectional survey data, this estimate was interpreted as a statistical decomposition of observed associations rather than evidence of causal mediation.</p> Conclusions <p>In this secondary data analysis of NHANES 2011–2020, self-reported sleep disorder status was associated with higher odds of tooth looseness, and continuous METS-IR statistically accounted for a modest proportion of this association. These findings suggest that metabolic dysfunction may be relevant to the association between sleep-related health and oral health. However, the results should be interpreted as cross-sectional, model-based associations rather than causal evidence. Longitudinal studies with objective sleep assessment, clinical periodontal evaluation, assessment of sleep bruxism, dietary assessment, and repeated metabolic measurements are needed to clarify temporality and potential causal relationships.</p>