Association between composite dietary antioxidant index and rheumatoid arthritis: results from NHANES 2003-2018

<b>Background</b>: Increasing evidence has revealed oxidative stress as an essential risk factor in the development of rheumatoid arthritis (RA). Composite dietary antioxidant index (CDAI) is an important tool for assessing dietary antioxidant capacity. However, the association between CDAI and RA is still unclear. <b>Method</b>: The data of 26501 participants from the NHANES database 2003-2018 cycle were collected to investigate the relationship between CDAI and RA risk. Logistic regression was used to examine the odds ratio (OR) of CDAI to RA risk. Restricted cubic spline (RCS) was utilized to test for potential nonlinear relationship. Stratified analysis and sensitivity analysis were also performed to strengthen the reliability of results. <b>Results</b>: Multivariate logistic regression with full adjustment for covariates showed that the OR (95% confidence interval (CI)) for CDAI to RA was 0.974 (0.955, 0.993). A nonlinear negative correlation was identified by the RCS (p for nonlinearity=0.046). In both the subgroup and sensitivity analysis, this relationship was still present. <b>Conclusion</b>: Our work suggests that higher dietary antioxidants intake is correlated with a lower RA incidence, thus providing some dietary recommendations for daily diets. Further clinical studies are acquired to better validate the current findings.