The comprehensive relationship between combined anti-inflammatory and healthy diets and all-cause mortality in rheumatoid arthritis: results from NHANES 2003-2018

Background: Rheumatoid arthritis (RA) is a chronic, systemic autoimmune inflammatory disorder. Diet is recognized as a modifiable factor that may influence inflammation and potentially accelerate RA progression. Nevertheless, the effects of diverse dietary patterns and their combined impact on RA progression and long-term mortality remain inadequately understood. This study examined the association between dietary patterns and mortality in patients with RA, focusing on the Healthy Eating Index (HEI-2015) and Dietary Inflammatory Index (DII) and evaluating their combined effects.

Methods: The analysis included 2,069 patients with RA from the National Health and Nutrition Examination Survey (NHANES) spanning 2003-2018. Weighted multi-variable Cox regression models estimated the relationship between the DII, HEI-2015, combined dietary patterns, and all-cause mortality in patients with RA. Linear associations between the DII, HEI-2015, and all-cause mortality were analyzed using restricted cubic splines (RCS). Dietary factors associated with mortality were identified through the Least Absolute Shrinkage and Selection Operator (LASSO) method, and subgroup and sensitivity analyses were conducted to strengthen the findings.

Results: Participants had a median age of 59 years (IQR: 48-69), with 42.1% male. Adjusting for potential confounders, the hazard ratio (HR) for individuals adhering to healthy and anti-inflammatory dietary patterns, as opposed to unhealthy and pro-inflammatory patterns, was 0.70 (95% CI: 0.53-0.92; adjusted P = 0.01; trend P = 0.02). In weighted Cox analyses of the DII and HEI-2015, higher quartiles showed no significant mortality risk difference from the lowest quartiles. The LASSO-Cox model identified 12 dietary components predictive of all-cause mortality in patients with RA, with an AUC of 0.749 (0.682-0.815) at 1 year, 0.763 (0.724-0.802) at 3 years, 0.783 (0.749-0.802) at 5 years, and 0.868 (0.712-0.938) for all death events. Kaplan-Meier analysis revealed that the low-risk dietary group exhibited significantly lower mortality compared to the high-risk group (P < 0.001).

Conclusions: These findings suggest that combining a higher HEI-2015 with a lower DII score correlates with reduced all-cause mortality risk among patients with RA, supporting dietary modification as a potential strategy to prevent premature death in this population.