Routine Serum Cortisol Does Not Predict Mortality or OMI/NOMI Differentiation in NSTEMI: A Prospective Emergency Department Cohort Study

Background/Objective: Risk stratification in non-ST-segment elevation myocardial infarction (NSTEMI) relies heavily on clinical parameters, while the prognostic utility of acute stress hormones remains unclear. This study aimed to evaluate the value of serum cortisol levels measured at emergency department (ED) presentation in predicting 30-day mortality and differentiating occlusion myocardial infarction (OMI) from non-occlusion myocardial infarction (NOMI). Methods This prospective observational cohort study included 150 consecutive patients presenting to a tertiary ED diagnosed with NSTEMI who underwent coronary angiography. Serum cortisol levels were measured upon admission. Patients were classified into OMI (TIMI 0–2, or TIMI 3 with specific criteria) and NOMI (TIMI 3) groups based on angiographic findings. The primary outcome was 30-day all-cause mortality. Results The cohort (mean age 59.9 ± 11.8 years; 71.3% male) comprised 125 (83.3%) OMI and 25 (16.7%) NOMI cases. 30-day mortality occurred in 8 (5.3%) patients. Median admission serum cortisol levels did not significantly differ between survivors and non-survivors (10.1 vs. 12.5 µg/dL, p = 0.298) or between the OMI and NOMI groups (10.2 vs. 10.8 µg/dL, p = 0.803). Conversely, mortality was significantly associated with elevated neutrophil-to-lymphocyte ratio (NLR) (p = 0.016), lymphopenia (p = 0.012), hypertension (p = 0.013), and higher GRACE scores (p < 0.001). Notably, the NOMI cohort had a significantly higher proportion of female patients compared to the OMI group (48.0% vs. 24.8%, p = 0.019). Conclusion Admission serum cortisol levels do not provide incremental diagnostic or prognostic value for OMI/NOMI differentiation or mortality prediction in NSTEMI patients. Routine clinical risk scores (GRACE) and hematological inflammatory indices (NLR, lymphopenia) offer significantly superior reliability. Therefore, routine cortisol measurement is not indicated for risk stratification in the fast-paced acute ED setting.