Correlation between CBC-derived inflammatory indicators and all-cause mortality with rheumatoid arthritis: a population-based study

Yu Liu¹Yiping Liu¹Shao Fan²Jing Yang¹Mingxi Xu¹Lin Zhao¹Changyan Liu^1*Yida Xing^1*Xiaodan Kong^1*

• ¹Second Affiliated Hospital of Dalian Medical University, Dalian, China
• ²Dalian Medical University, Dalian, Liaoning, China

Objective: We investigated the relationship between inflammatory indicators derived from complete blood cell (CBC) counts and all-cause mortality in individuals with rheumatoid arthritis (RA).Methods: Data were collected from the National Health and Nutrition Examination Survey (NHANES) database from 2007 to 2018, with a median follow-up duration of 78 months. The inflammatory indicators derived from CBC included several types: the systemic inflammatory response index (SIRI), the systemic immune-inflammation index (SII), the neutrophil-to-lymphocyte ratio (NLR), the plateletto-lymphocyte ratio (PLR), and the monocyte-to-lymphocyte ratio (MLR). The multiple COX regression models were used to estimate adjusted hazard ratios (HRs) and 95% CIs concerning allcause mortality of participants with RA, which focused on CBC-derived inflammatory indicators.Additionally, restricted cubic spline (RCS) curve was utilized to investigate nonlinear associations.The research comprised a cohort of 1,314 individuals, among whom 246 with RA succumbed during a median follow-up duration of 78 months. After adjusting for key covariates, the mortality rate in patients with RA who had high SIRI, NLR, and MLR levels was considerably higher than in those with medium or low SIRI, NLR, and MLR levels. Compared with the lowest tertile, the highest tertiles of SIRI (HR 1.87, 95% CI: 1.12-3.13), NLR (HR 1.79, 95% CI: 1.10-2.92), and MLR (HR 1.88, 95% CI: 1.17-3.02) were associated with an increased risk of all-cause mortality. The Kaplan-Meier analysis indicated a significant decrease in the survival probability among individuals with elevated SIRI, NLR, and MLR levels. The RCS analysis revealed a linear association between SIRI, NLR, MLR, and RArelated all-cause mortality, whereas a nonlinear relationship was identified between the SII, PLR, and mortality.This investigation revealed that the SIRI, NLR, and MLR are novel, valuable, and convenient inflammatory indicators. In the U.S. adults with RA, higher SIRI, NLR, and MLR were independently associated with an increased long-term mortality risk. These findings not only assist in uncovering the potential utility of predicting RA outcomes but also provide rheumatologists valuable guidance for disease management.