Association Between C‐Reactive Protein‐Triglyceride Glucose Index, and the Risk of Osteoarthritis and Rheumatoid Arthritis: Results From <scp>NHANES</scp> 1999–2010

The serum C-reactive protein-triglyceride glucose index (CTI) is a parameter integrating inflammation and insulin resistance, which are potential mechanisms for osteoarthritis (OA) or rheumatoid arthritis (RA). Our study aims to investigate its association with the risk of OA or RA. This study is based on cross-sectional data from the National Health and Nutrition Examination Survey (NHANES) 1999-2010, involving 6395 participants aged ≥ 20 years. Weighted logistic regression, restricted cubic splines (RCS), and subgroup analysis were employed to assess the relationship between CTI and OA, RA. After adjusting for confounding factors, CTI showed a significant positive correlation with the risk of OA (p < 0.05), and a non-linear relationship was observed (p = 0.0069). The risk of OA peaked when CTI reached 8.35 and gradually declined beyond this threshold. Subgroup analyses confirmed that this association consistently existed across different populations (all interaction p > 0.05). For RA, after adjustment for metabolic and lifestyle factors, the association between CTI and RA was not statistically significant (p > 0.05). There is a significant non-linear association between CTI and the risk of OA, suggesting that CTI may serve as a comprehensive indicator for assessing OA risk.