Abstract Body (Do not enter title and authors here): Introduction/Background: Vitamin D deficiency has been associated with various cardiovascular and neurological conditions, but its impact on outcomes following subarachnoid hemorrhage (SAH) remains poorly understood. Given vitamin D's role in neuroprotection and inflammation modulation, we hypothesized that vitamin D deficiency would be associated with worse clinical outcomes in SAH patients.

Research Questions/Hypothesis: Is vitamin D deficiency associated with increased mortality and neurological complications compared to normal vitamin D levels in patients following nontraumatic subarachnoid hemorrhage?

Methods/Approach: We retrospectively identified patients with nontraumatic subarachnoid hemorrhage using 2022 Electronic Health Record data from the TriNetX US Collaborative Network encompassing 69 healthcare organizations. Patients were categorized into two cohorts based on serum calcidiol levels measured within 6 months of SAH diagnosis: vitamin D deficient (≤20.0 ng/mL, n=4,326) and normal vitamin D (30.0-50.0 ng/mL, n=5,936). One-to-one propensity score matching was performed for age, sex, race/ethnicity, diabetes, hypertension, dyslipidemia, body mass index, smoking status, and alcohol use disorders, yielding 3,663 patients per cohort. Outcomes were assessed over a 3-year follow-up period using survival analysis for mortality and risk analysis for neurological complications.

Results/Data: After propensity matching, cohorts had similar baseline characteristics (mean age 59.9 years, 51.6% female, 63.7% White). Vitamin D-deficient patients demonstrated significantly higher mortality (23.4% vs 17.5%, p<0.001) with a hazard ratio of 1.424 (95% CI: 1.286-1.578). Vitamin D deficiency was associated with increased risk of hydrocephalus (8.8% vs 7.2%, OR=1.255, 95% CI: 1.059-1.488, p=0.009) and cerebral edema (7.4% vs 5.9%, OR=1.280, 95% CI: 1.064-1.540, p=0.009). No significant differences were observed in seizure rates, craniotomy requirements, or paralysis outcomes between groups.

Conclusion(s): Vitamin D deficiency is associated with 42% increased mortality risk and higher rates of hydrocephalus and cerebral edema following subarachnoid hemorrhage. These findings suggest vitamin D status may be an important modifiable risk factor for SAH outcomes, warranting consideration of vitamin D screening and potential supplementation in SAH management protocols.