Association between the triglyceride-glucose-waist-to-height ratio index and mortality in patients with hypothyroidism: A retrospective cohort study based on NHANES

This study aimed to investigate the association between the triglyceride-glucose (TyG) waist-to-height ratio (WHtR) index and mortality risk among individuals with hypothyroidism. Building on prior evidence linking insulin resistance and central obesity to adverse health outcomes, this research specifically sought to evaluate whether the combined metric of TyG-WHtR (integrating triglyceride-glucose index and waist-to-height ratio) holds enhanced predictive utility for mortality in a nationally representative sample of United States adults with hypothyroidism. Using data from the 2007 to 2012 National Health and Nutrition Examination Survey, we included 8437 adults. Multivariable logistic regression was used to assess the association between TyG-WHtR and hypothyroidism prevalence. Multivariable Cox regression models, restricted cubic splines, and subgroup analyses with Bonferroni correction (significance threshold α′ = 0.0071) were employed to evaluate mortality risks. Predictive performance was assessed using receiver operating characteristic and time-dependent receiver operating characteristic analyses. Higher TyG-WHtR quartiles were independently associated with an increased prevalence of hypothyroidism (Model 3, Q4 vs Q1: odds ratio [OR] = 1.62, 95% confidence interval [CI]: 1.20–2.18; P trend < .001). Among patients with hypothyroidism, the highest TyG-WHtR tertile (T3) was significantly associated with increased risks of all-cause mortality (hazard ratio [HR] = 2.40, 95% CI: 1.07–5.41) and cardiovascular disease (CVD) mortality (HR = 1.13, 95% CI: 1.02–1.29), whereas the moderate tertile (T2) showed no significant association (all-cause: HR = 1.59, 95% CI: 0.82–3.08; CVD: HR = 1.30, 95% CI: 0.60–1.49). Restricted cubic splines confirmed a positive linear association between TyG-WHtR and mortality outcomes (both P overall < .05). After Bonferroni correction, a significant interaction was maintained only for body mass index in relation to all-cause mortality ( P interaction < .007). The TyG-WHtR index demonstrated stable predictive power, with a 3-year area under the curve (AUC), 5-year AUC and 10-year AUC of 0.736, 0.725 and 0.714 for all-cause mortality and 0.675 (3-year), 0.652 (5-year), and 0.609 (10-year) for CVD mortality, respectively. This study provides new evidence for risk stratification using the TyG-WHtR index in the hypothyroid population. An elevated TyG-WHtR index is not only associated with a higher prevalence of hypothyroidism, but also serves as a stable and independent predictor of all-cause and CVD mortality.