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Association between systemic immune-inflammation index and in-hospital mortality in ICU patients with aspiration pneumonia: A retrospective cohort study based on MIMIC-IV database

Nan Liu, Hong Zhou

Therapeutic Advances in Respiratory Disease, 2026

2,132 participants

Abstract

Background Aspiration pneumonia is a common and life-threatening condition among critically ill patients, with mortality reaching 20–50%. The Systemic Immune-Inflammation Index (SII), derived from the routine complete blood count, has shown prognostic value in various inflammatory and infectious diseases, but its association with outcomes in ICU patients with aspiration pneumonia is unknown. Objectives To investigate the association between SII and in-hospital mortality in ICU patients with aspiration pneumonia and to characterize the dose-response relationship. Design Retrospective cohort study using a large publicly available critical care database. Methods Adult patients (≥18 years) admitted to the ICU with aspiration pneumonia and an ICU stay ≥24 hours were identified in the MIMIC-IV database (version 3.1). SII (neutrophil × platelet/lymphocyte count) was derived from laboratory values obtained within the first 24 hours of admission and stratified into quartiles. Multivariable logistic regression with sequential adjustment evaluated the association with in-hospital mortality; restricted cubic splines characterized the dose-response relationship, and subgroup and sensitivity analyses assessed robustness. Results A total of 2,132 patients were included (median age 66 years, IQR 54–78; 62.2% male); overall in-hospital mortality was 25.5%. Mortality across SII quartiles was 24.6% (Q1), 20.5% (Q2), 26.1% (Q3) and 31.0% (Q4), exhibiting a U-shaped pattern. Using Q2 as…

How strong is the evidence?

Evidence Hub reads this as a cohort study, done in people. Its evidence level is 3 of 5 (Moderate · trial / cohort / secondary analysis). Trials without a large randomized design, cohorts and secondary analyses give moderate evidence. Reported size: 2,132 participants or records.

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