Prognostic value of systemic immune-inflammation index to albumin ratio (SAR) for long-term all-cause mortality in sepsis survivors: evidence from a multicenter cohort with up to 6 years of follow-up

Patients recovering from sepsis still face a higher long-term mortality risk. This study aims to explore the association between the systemic immune-inflammation index-to-albumin ratio (SAR) and the risk of long-term all-cause mortality (up to 6 years) in sepsis survivors. Between January 2017 and December 2022, 461 participants with sepsis recurrence-free status for at least 3 months following the first-episode sepsis cure from Nanning Third People’s Hospital, Guangxi Medical Sciences Academy and the People’s Hospital of Guangxi Zhuang Autonomous Region, were enrolled. Participants were categorized into three groups based on SAR tertiles: low-level (< 32.15, n = 153), moderate-level (32.15–80.57, n = 154), and high-level (> 80.57, n = 154). All participants were followed up every 3 months for a median of 36 months up to 6 years. The relationships between SAR and all-cause mortality risk were analyzed. Of the 461 participants, 177 (38.4%) died. Multivariable Cox regression analysis showed that the high-level SAR group had a higher risk of all-cause mortality in model III (P = 0.014). Subgroup stratification analysis revealed that when grouped by SAR level tertiles (with the lowest tertile as the reference baseline for all-cause mortality, a hazard ratio (HR) = 1), each subsequent tertile increase in SAR level was associated with a 21.9% higher risk of all-cause mortality in patients aged ≥ 65 years (HR = 1.219, 95% CI = 0.954–1.558, P for interaction < 0.001), and a 26.1% higher risk in those with cardiovascular and cerebrovascular complications (HR = 1.261, 95% CI: 0.925–1.719, P for interaction < 0.001), respectively. Kaplan-Meier analysis indicated that higher SAR levels were associated with lower survival probability (log-rank, P = 0.00025). The restricted cubic spline (RCS) model identified an inverted J-shaped dose-dependent relationship between SAR level and all-cause mortality risk (P for overall < 0.0001). Receiver operating characteristic (ROC) analysis demonstrated an optimal SAR cutoff value of 113.561 for predicting all-cause mortality. Decision curve analysis (DCA) confirmed that SAR provided a greater net clinical benefit than existing indicators, such as the systemic immune-inflammation index (SII), red blood cell distribution width (RDW), and lymphocyte to high-density lipoprotein cholesterol ratio (LHR). The findings suggest that SAR may serve as a potential cofactor, alongside age and cardiovascular comorbidities, in clinical decision-making regarding long-term all-cause mortality risk in sepsis survivors.