Admission 25-Hydroxyvitamin D Deficiency Is Associated with Poor Outcomes in ICU Patients with Sepsis-Associated Encephalopathy (SAE)

Background: Sepsis-associated encephalopathy (SAE) is a serious complication affecting septic patients and significantly increases mortality. Serum 25-hydroxyvitamin D (vitamin D) deficiency is prevalent in critical illness, but its relationship with SAE prognosis remains unclear. Methods: This retrospective cohort study enrolled SAE patients at Nanjing Drum Tower Hospital (January 2023–June 2024). Vitamin D levels were measured within 24 h of ICU admission with insufficiency and deficiency defined as ≤30 ng/mL and ≤20 ng/mL, respectively. Demographics, severity scores, laboratory parameters, organ support, and 90-day mortality were collected. Statistical analyses included Mann–Whitney U/t-tests, Spearman’s correlation, multivariate logistic regression, and ROC analysis. Results: Among 346 sepsis patients, 47 met SAE criteria. Vitamin D insufficiency affected 97.9% (46/47) of SAE patients, with 85.1% (40/47) being deficient. Ninety-day mortality was 25.5% (12/47). Non-survivors had significantly lower vitamin D levels than survivors (median 10.15 vs. 12.83 ng/mL, p = 0.010). Multivariate analysis identified higher APACHE II score (OR 1.164, 95% CI 1.042–1.300; p = 0.007) and lower vitamin D level (OR 0.758, 95% CI 0.603–0.954; p = 0.018) as independent predictors of 90-day mortality. Combining APACHE II score and vitamin D provided excellent predictive value (AUC 0.886). Vitamin D levels correlated negatively with IL-6 (rho = −0.293, p = 0.045) and vasopressor use (rho = −0.410, p = 0.004). Conclusions: Vitamin D insufficiency is nearly universal in SAE patients. Lower admission vitamin D levels independently predict 90-day mortality and enhance the predictive power of APACHE II. Vitamin D levels were negatively correlated with IL-6, suggesting a potential relationship with inflammation, but causality and clinical significance require further investigation.