Association between dietary inflammatory index scores and the increased disease activity of rheumatoid arthritis: a cross-sectional study

BACKGROUND: Diet plays an important role in regulating inflammation, which is a hallmark of rheumatoid arthritis (RA). Our aim was to investigate the association between the Dietary Inflammatory Index (DII) scores and RA activity. METHODS: This cross-sectional study was conducted on 184 patients with RA in rheumatology clinic in Kermanshah city, Iran, in 2020. RA was diagnosed according to the criteria of the 2010 American College of Rheumatology/ European League against Rheumatism. The overall inflammatory potential of the diet was extracted from a validated 168-item food frequency questioner (FFQ) using the DII. RA disease activity was assessed using Disease Activity Score 28 (DAS-28) scores. Logistic regression and one-way ANOVA/ ANCOVA were conducted. RESULTS: Individuals in the highest DII quartile had the significantly higher odds of positive C-reactive protein than those in the lowest quartile of the DII scores (OR 4.5, 95% CI 1.16 – 17.41, P = 0.029). A statistically significant downward linear trend in fat-free mass and weight were observed with increasing the DII quartiles (P = 0.003, P = 0.019, respectively). Patients in the highest DII quartile had higher DAS-28 scores than those in the first quartile (Mean difference: 1.16, 95% CI 0.51 – 1.81, P < 0.001) and second quartile of the DII scores (Mean difference: 1.0, 95% CI 0.34 – 1.65, P < 0.001). CONCLUSION: Our results indicated that reducing inflammation through diet might be one of the therapeutic strategies to control and reduce the disease activity in RA patients.