Association between body roundness index and rheumatoid arthritis: a cross-sectional study based on NHANES

Background The Body Roundness Index (BRI) has been identified as a potentially superior measure of body fat distribution such as body mass index (BMI) and waist circumference (WC). However, its relationship with rheumatoid arthritis (RA) has yet to be thoroughly investigated. This study examines the association between BRI and RA risk using data from the National Health and Nutrition Examination Survey (NHANES). Methods The analysis included 28,559 adults, excluding those with missing values for BRI or RA status. BRI was calculated using height and WC measurements, while RA was self-reported by participants. Multivariate logistic regression was utilized to assess the relationship between BRI and RA, while controlling for sociodemographic variables and pertinent comorbid conditions. Receiver operating characteristic (ROC) curves and the area under the curve (AUC) were employed to assess the predictive accuracy of BRI, BMI, and WC concerning RA. Results An elevated BRI demonstrated a notable correlation with a heightened risk of RA. With each unit increase in BRI, there was a corresponding 10% increase in the likelihood of RA after complete adjustment (OR: 1.10, 95% CI: 1.08–1.12, P < 0.001). A clear dose-response relationship was identified among the BRI quartiles, where individuals in the highest quartile exhibited a 76% increased risk (OR: 1.76, 95% CI: 1.50–2.07, P < 0.001). Subgroup analysis indicated a more pronounced association among participants exhibiting hyperlipidemia (P for interaction = 0.012). Threshold analysis revealed a BRI value of 4.61 as the critical inflection point, beyond which each unit increase correlated with a 12% elevated risk of RA (OR: 1.12, P < 0.001). ROC analysis revealed that BRI exhibited the highest AUC of 0.637 in predicting RA risk, surpassing WC at 0.622 and BMI at 0.594. Conclusions BRI serves as a strong indicator of RA risk, demonstrating enhanced predictive accuracy when contrasted with conventional metrics like BMI and WC. The results indicate that BRI may function as a valuable instrument for assessing the risk of RA, especially in those exhibiting hyperlipidemia.