Nonlinear association and predictive value of stress hyperglycemia ratio for 28-day in-hospital mortality in patients with acute hypoxemic respiratory failure

Stress hyperglycemia ratio (SHR), calculated as admission glucose divided by estimated average glucose from glycated hemoglobin, has emerged as a reliable biomarker of physiological stress. However, its prognostic role in acute hypoxemic respiratory failure (AHRF) - particularly the potential nonlinear relationship with short-term mortality - remains underexplored. This study aimed to evaluate the nonlinear association and predictive value of SHR for 28-day in-hospital mortality in AHRF patients. A retrospective cohort study was conducted using data from the medical information mart for intensive care version 3.1 database (2008-2019). Patients with AHRF (ICD-10 code: J9601) were included. Propensity score matching (1:1) was applied to balance baseline characteristics (sex, age, comorbidities) between high and low SHR groups. The primary outcome was 28-day in-hospital mortality. Restricted cubic spline models explored dose-response relationships. Kaplan-Meier survival curves, multivariable Cox regression, and subgroup analyses were used to assess associations. A total of 704 patients were included, with 614 successfully matched after propensity score matching. Restricted cubic spline analysis revealed a significant nonlinear association between SHR and 28-day mortality (P for overall = .002; P for nonlinearity = .002), with a critical inflection point at 1.215. Patients with SHR > 1.215 (high SHR group) had a significantly increased mortality risk (hazard ratio [HR] = 1.508, 95% confidence interval: 1.184-1.922; log-rank P < .001). Subgroup analyses confirmed consistent associations across most subgroups (e.g., age, sex, diabetes), with no significant interactions (all P > .05). Notably, the association was amplified in patients with prior myocardial infarction or congestive heart failure (interaction P = .021). SHR exhibits a nonlinear association with 28-day in-hospital mortality in AHRF patients, with a critical threshold at 1.215. It serves as a simple, accessible tool for early risk stratification, particularly in those with cardiovascular comorbidities.