The association between geriatric nutritional risk index (GNRI) and immune-inflammatory biomarkers in elderly rheumatoid arthritis: Insights based on NHANES 2005–2018

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disorder, leading to long-lasting pain. This study aimed to explore the relationship between geriatric nutritional risk index (GNRI) and immune-inflammatory biomarkers neutrophil-percentage-to-lymphocyte ratio (NPAR)/neutrophil-to-lymphocyte ratio (NLR)/platelet-to-lymphocyte ratio (PLR)/lymphocyte-to-monocyte ratio (LMR)/systemic immune-inflammation index (SII) in elderly RA patients. We analyzed data from the National Health and Nutrition Examination Survey (NHANES; 2005-2018), focusing on adults aged ≥60 years (final sample size = 6848). In this cross-sectional study, a total of 1057 individuals were identified with RA, and 5791 were classified as non-RA. Univariate logistic regression analysis was performed to investigate the association between GNRI, NPAR/NLR/PLR/LMR/SII, covariates and RA. Then multivariable logistic regression analysis was carried out to detect the relationship between GNRI and NPAR/NLR/PLR/LMR/SII. Their nonlinear relationships were explored by restricted cubic splines. Significant differences in demographic and clinical characteristics were observed between RA and non-RA groups, particularly in age, gender, race, education, marital status, etc (P < .05). In RA participants, significantly more females were observed, and there were more participants with higher body mass index. Moreover, 78.9% of RA participants had hypertension. Comparing to non-RA samples, there were significantly lower NLR, PLR, SII levels in RA participants. Logistic regression analysis revealed associations between higher RA risk and various factors, including higher BMI, hypertension, and lower education levels. GNRI was significantly associated with NLR (odds ratio [OR] of model 3 = 1.32, 95% confidence interval [CI] = 1.15-1.51)/PLR (OR of model 3 = 1.01, 95% CI = 1.00-1.01)/LMR (OR of model 3 = 0.85, 95% CI = 0.76-0.94)/SII (OR of model 3 = 1.00, 95% CI = 1.00-1.00) in elderly RA. Nonlinear relationships between GNRI and these biomarkers were also identified, highlighting the complexity of their interactions. In elderly RA, significant nonlinear correlation has been revealed between GNRI and immune-inflammatory biomarkers NLR, PLR, LMR, SII.