Systemic immune-inflammation index, Systemic immune response index, Osteoarthritis, NHANES, ln-SII, RCS, Diseases of the musculoskeletal system, RC925-935

Background: Investigate the link between systemic immune-inflammatory index (SII) and Systemic Immune Response Index (SIRI) with osteoarthritis (OA) using National Health and Nutrition Examination Survey (NHANES) data (1999–2018). Methods: Extracted NHANES data (1999–2018) and selected a study population based on demographic, examination, and laboratory data. Calculated SII (platelet count ​× ​neutrophil count/lymphocyte count) and SIRI (neutrophil count ​× ​monocyte count/lymphocyte count). Employed multivariate logistic regression and restricted cubic spline (RCS) regression for Ln-SII, SIRI, and OA relationship investigation. Conducted subgroup analyses. Results: Study involved 32,144 participants (16,515 males, 15,629 females), with 12.16% having OA. Positive correlation between highest SII quartile and OA in unadjusted and adjusted model 1 (Unadjusted Model, P ​ ​0.05). Conclusion: When SII exceeds 595.86, OA prevalence may rise. Besides, there was a significant positive correlation between SIRI and OA prevalence. SII and SIRI may be useful markers for OA research, warranting further exploration in this area.