Association between erythrocyte distribution width and albumin ratio and rheumatoid arthritis: the mediating role of obesity

Purpose This study utilized NHANES data from 1999 to 2010 to examine the association between the red cell distribution width to albumin (RAR) ratio and rheumatoid arthritis (RA) while also exploring the mediating role of obesity in this relationship. Patients and methods: We analyzed 27,418 NHANES participants, calculating RAR as red cell distribution width (%) divided by albumin concentration (g/dL). RA diagnoses were based on questionnaire data. Multivariate regression and subgroup analyses were conducted to assess the RAR-RA association, and smoothing curve fitting was used to examine nonlinear relationships. Furthermore, the analysis revealed that obesity significantly mediates the association between RAR and RA. Results RA was diagnosed in 5.72% of the population. Higher RAR levels were significantly associated with increased RA prevalence (OR = 2.07; 95% CI: 1.57–2.72; p < 0.001), particularly in younger age groups and those using steroids. A nonlinear relationship was observed, with stronger associations at RAR levels below 3.13. Mediating effect analysis showed that body mass index mediated 28.62% of the relationship between RAR and RA, while body roundness index mediated 22.41%. Conclusion The prevalence of RAR is positively correlated with RA, with obesity playing a significant mediating role in this association.