Association between stress hyperglycemia ratio and mortality of traumatic brain injury patients based on MIMIC-IV and eICU databases

To investigate the association between the stress hyperglycemia ratio (SHR) and short-term mortality, including 28-day and ICU mortality, in patients with traumatic brain injury (TBI). Data from the MIMIC-IV and eICU databases were used as the training and validation cohorts, respectively. Patients were stratified into SHR quartiles. Cox regression models (adjusted for age, sex, SOFA, APS III, heart failure, GCS, ventilator duration, neurosurgical intervention, and injury-to-ICU time) and Kaplan–Meier curves were applied to assess associations between SHR and mortality. Restricted cubic spline (RCS) models examined dose–response patterns, and subgroup analyses evaluated potential effect modification. In the MIMIC-IV cohort, SHR was positively associated with SOFA and APS III scores (both P < 0.001). Cox regression and Kaplan–Meier analyses demonstrated that higher SHR was significantly associated with increased 28-day all-cause mortality (fully adjusted HR for highest vs. lowest quartile: 1.83, 95% CI 1.18–2.87). Similar associations were observed in the external eICU cohort (adjusted HR: 2.32, 95% CI 1.01–5.36). Restricted cubic spline analysis showed a nonlinear relationship between SHR and 28-day mortality, with a mathematical inflection point around SHR ≈ 1.3. Subgroup analyses indicated that the association between SHR and 28-day mortality was stronger in male patients (HR 2.01, 95% CI 1.23–3.29) and in those with lower APS III scores (HR 4.02, 95% CI 1.39–11.64) (both P for interaction < 0.05).In contrast, although crude Kaplan–Meier curves showed higher ICU mortality in the upper SHR quartiles, the association between SHR and ICU mortality was not statistically significant in fully adjusted Cox models in either cohort. SHR was strongly associated with 28-day all-cause mortality in TBI patients. However, its association with ICU mortality was not statistically significant after adjustment and should be considered inconclusive.