The association between composite dietary antioxidant index and rheumatoid arthritis: evidence from NHANES 2001-2020

Background This study aimed to investigate the relationship between the composite dietary antioxidant index (CDAI) and rheumatoid arthritis (RA) using data from the National Health and Nutrition Examination Survey (NHANES) spanning from 2001 to 2020. Methods CDAI is based on the intake of vitamins A, C, E, manganese, selenium, and zinc from the diet. RA patients were identified through questionnaire responses. Weighted multivariate regression analysis was employed to examine the association between CDAI and RA. Additionally, restricted cubic splines were utilized to assess potential non-linear relationships. Subgroup analyses were used to explore whether the relationship between CDAI and RA remained consistent across subgroups (e.g., sex, age, smoking status, etc.). We also used interaction terms to assess whether these subgroup variables influence the relationship between CDAI and RA risk. Finally, we also performed sensitivity analyses to assess the robustness of the main findings after excluding patients with a history of diabetes. Results The study included a total of 11,266 patients. After adjusting for all covariates, the multivariate logistic regression analysis showed that each unit increase in CDAI was associated with a 4% reduction in the odds of RA (odds ratio = 0.96, 95% confidence interval = 0.94-0.99). The incidence of RA was found to decrease as CDAI levels increased (P for trend < 0.05). In the restricted cubic spline analysis, a linear relationship between CDAI and RA was observed. Subgroup analyses and interactions demonstrated that the negative association between CDAI and RA was consistent across all subgroups and was influenced by smoking. Conclusion This study indicates a negative correlation between CDAI and RA, suggesting that CDAI may serve as a valuable and convenient marker for reducing the risk of RA in US adults. Clinical trial number Not applicable.