The Role of High Serum Apelin Levels Within the First 24 h in Predicting 28-Day and Long-Term Mortality in Ischemic Cerebrovascular Disease

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Background/Objectives: The apelin/APJ system has demonstrated neuroprotective effects in experimental studies by regulating key pathogenic mechanisms of ischemic stroke, including oxidative stress, apoptosis, cerebral edema, and inflammation. This study aimed to investigate the role of serum apelin levels measured within the first 24 h in predicting 28-day and long-term mortality in patients with ischemic cerebrovascular disease. Methods: This prospective cohort study included 44 patients hospitalized with a diagnosis of acute ischemic stroke due to large artery atherosclerosis. Serum apelin levels were measured using the ELISA method from blood samples obtained within the first 24 h after symptom onset. Patients were prospectively followed for 28-day and long-term mortality. Results: During the follow-up period, 32.6% of the patients died. The median serum apelin level was significantly higher in the deceased group compared to the survivors [105.0 pg/mL vs. 55.8 pg/mL]. In ROC analysis, the area under the curve (AUC) for apelin in predicting mortality was 0.727 (95% CI: 0.550–0.903). The optimal cut-off value was determined as ≥70.47 pg/mL (sensitivity: 85.71%, specificity: 62.07%). In Kaplan–Meier analysis, the 28-day mortality rate was 52.2% in the high-apelin group (≥70.47 pg/mL), whereas it was 10.0% in the low-apelin group (<70.47 pg/mL) (p = 0.004). In multivariate Cox regression analysis, an apelin level <70.47 pg/mL was identified as an independent prognostic factor (HR: 0.16; 95% CI: 0.03–0.94). The cumulative survival rates at days 28, 56, and 180 were 56.1%, 46.7%, and 11.7%, respectively, in the high-apelin group, while these rates were 100%, 100%, and 81.8%, respectively, in the low-apelin group. The mean NIHSS score was significantly higher in the high-apelin group, and a strong, positive, and highly significant correlation was found between serum apelin level and NIHSS score (r = 0.703, p < 0.001). Conclusions: High serum apelin levels measured within the first 24 h in acute ischemic stroke are associated with increased 28-day and long-term mortality. The association of high endogenous apelin levels with poor prognosis in the clinical setting suggests that apelin is mobilized as a stress response during ischemia, and that elevated circulating levels may actually reflect the severity of the ischemic insult.