Depression represents one of the most prevalent comorbid conditions among individuals with rheumatoid arthritis (RA). The triglyceride-glucose (TyG) index, recognized as a reliable surrogate marker for insulin resistance (IR), has yet to be thoroughly examined in terms of its association with depressive symptoms in RA patients. This study seeks to investigate the potential correlation between the TyG index and depression in this patient population.

This study analyzed data from the NHANCES database from 2005-2018 and included 576 rheumatoid arthritis patients aged 20 years or older. Depression was assessed using the Patient Health Questionnaire-9 (PHQ-9) score. Spearman correlation analysis was employed to evaluate the association between PHQ-9 scores and various TyG-related indices, including the TyG index, TyG-body mass index (TyG-BMI), TyG-waist circumference (TyG-WC), and TyG-waist-to-height ratio (TyG-WHtR). Multivariate regression analysis was performed to investigate the relationship between these TyG-related indices and depression among individuals with RA, while restricted cubic spline (RCS) analysis was applied to explore possible nonlinear associations. Subgroup analyses were conducted to validate the consistency of this association across different demographic and clinical subpopulations.

The study finally included 576 patients with RA, of which 209 (36.28%) were diagnosed with depression (PHQ-9>4). Compared with patients without depression, those with depression have higher levels of TyG-BMI (270.188 (222.066,332.677) vs. 253.910 (220.223,303.139), p=0.048), and TyG-WHtR (5.646 (4.856,6.532) vs. 5.364 (4.754,6.089), p=0.018) , but not TyG and TyG-WC (917.740 (807.177,1078.274) vs. 898.217(799.423,1020.872), p=0.234)). The results of the multivariate regression analysis indicated that only TyG-WhtR was independently associated with the occurrence of depression in RA patients, even after adjusting for all confounding factors. Patients in the third tertile of TyG-WHtR had a 93.4% increased risk of developing depression compared to those in the first tertile. Subgroup analysis indicated no significant interaction effects. 

This study has confirmed the close correlation between TyG-WHtR and the occurrence of depression in the RA population.