Investigating the relationship between energy-adjusted dietary inflammatory index with anthropometric indices, clinical symptoms, inflammatory markers, sleep quality and quality of life in patients with rheumatoid arthritis: a cross-sectional study

Rheumatoid arthritis (RA) is a chronic autoimmune disease causing joint inflammation, pain, and deformity, significantly impacting physical and mental well-being. Sleep disturbances and obesity exacerbate symptoms, increasing disease severity. Inflammation plays a key role in RA progression, and diet may influence inflammation. The Dietary Inflammatory Index (DII) reflects the inflammatory potential of dietary intake, but its link to RA symptoms is unclear. This study explores DII associations with RA outcomes, sleep quality, anthropometric indices, and quality of life (QoL). This cross-sectional study included 246 RA patients attending a rheumatology clinic in Ahvaz, Iran. Dietary intake was assessed using a validated food frequency questionnaire, and the energy-adjusted Dietary Inflammatory Index (E-DII) was calculated. To analyze the data, we employed various statistical methods, including analysis of variance, chi-square tests, linear and Poisson regression, as well as logistic regression, as appropriate. In this study, patients with RA (163 females and 83 males; mean age 50.40 ± 6.33 years) were evaluated. Higher E-DII was significantly associated with higher poor sleep quality across all models (OR = 1.49, 95% CI: 1.14-1.95). Higher E-DII scores were significantly associated with increased odds of both general obesity (OR = 1.77, 95% CI: 1.32-2.30) and central obesity (OR = 1.80, 95% CI: 1.31-2.47). Additionally, our results demonstrated that higher E‑DII scores were significantly and directly associated with disease activity scores, CRP levels, and tender joint counts. Our study suggests that among RA patients, a higher intake of pro-inflammatory diet is linked with a higher likelihood of sleep deprivation, increased general and central obesity, and an increased tender joint counts. Further longitudinal studies are necessary to confirm these findings and elucidate the relationship between the E-DII and these outcomes in RA patients.