Background Encephalitis (inflammation of the brain) is primarily divided into Autoimmune Encephalitis (AE) and Infectious Encephalitis (IE). Encephalitis poses a substantial burden on the U.S. healthcare system with an annual prevalence of 5-10 patients per 100,000 individuals and an inpatient mortality of nearly 10% 1-3. Additionally, most patients are discharged with sequelae of impaired cognitive function 4. Previous studies suggest both autoimmune (e.g. multiple sclerosis) and infectious (e.g. SARS-CoV-2) condition severity is associated with Vitamin D (VitD), where it can modify disease activity or where hypovitaminosis is a causal risk 5-6. VitD supplementation, an extremely accessible and cost-effective intervention, in some cases resulted in disease prevention and risk reduction 5,6. Despite these findings, the relationship between VitD and both autoimmune- and infection-mediated encephalitis is unknown. We sought to assess this relationship between VitD and clinical measures and outcomes in patients with encephalitis.

Methods 373 adult encephalitis patient charts from 03-31-2013 to 03-31-2023 were reviewed from the Texas Medical Center/Greater Houston area. VitD levels, demographics, physical exam findings, treatments, imaging findings, diagnostics, and outcome variables were collected. VitD values were trichotomized into “Deficient”, “Insufficient”, and “Sufficient” 7.

Results Chi Square Tests of Independence analysis revealed significant associations between VitD Status and Disposition (p = 0.01), Cause of Death (p < 0.001), and # Rituximab therapies (p = 0.006). Additionally, statistically significant associations existed between low VitD levels (VitD Deficiency and Insufficiency) and immunocompromised state (p = 0.008), poorer outcomes referencing the Glasgow Outcome Scale (GOS) (p = 0.014), Hospital Readmission (p < 0.001), severe comorbid conditions referencing the Charlson Comorbidity Score (p = 0.032), and Mortality (p < 0.001). Binary Regression analysis revealed confounds; African-American patients and those receiving mechanical ventilation had poorer outcomes based on the GOS (p = 0.008, 0.048).

Conclusion Our study provides evidence that VitD status has a significant relationship with AE and IE clinical measures and outcomes post-hospitalization. However, we were limited by lack of VitD documentation; ~10% of study patients had documented measurements taken during their hospital stay. This illuminates the need for clinicians to 1) collect VitD data for all AE/IE patients and 2) consider VitD supplementation, an accessible and cost-effective intervention, for AE/IE patients. Future studies, currently being pursued, include incorporating 300 additional AE/IE patients from the Johns Hopkins medical system to further define the relationship between VitD status with clinical outcomes.

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