Association between vitamin D deficiency and subarachnoid hemorrhage: a systematic review.

Introduction: Vitamin D functions also include regulating blood pressure and supporting the health of endothelial and brain cells. As such, vitamin D levels may be a determining factor for the occurrence of subarachnoid hemorrhage (SAH). Objective: This study aims to investigate the relationship between low vitamin D levels and the occurrence of SAH, particularly non-traumatic cases. Methods: Following PRISMA guidelines, we conducted a systematic review of studies published from 2008 to April 2023 in various databases, including SciELO, PubMed, EBSC HOST, and Google Scholar. We analyzed the data from 11 studies that measured serum levels of 25(OH)D (vitamin D) and attempted to correlate them with SAH occurrence. Results: Of the 11 studies reviewed, 9 supported the hypothesis that vitamin D deficiency or insufficiency increases the risk of developing SAH and other cerebrovascular diseases. However, two studies found no significant evidence to support this relationship, instead suggesting that SAH manifestation is independent of serum vitamin D levels. Discussion: Given the presence of the vitamin D receptor in various tissues, including the subarachnoid space vessels, it is clear that vitamin D plays a critical role in maintaining vascular function, vasoconstriction, vasodilation, endothelial remodeling, hypertension control, and inflammatory processes. Therefore, vitamin D deficiency is a risk factor for SAH occurrence. Conclusion: Our study highlights the importance of exploring vitamin D deficiency as a preventable risk factor for SAH occurrence and suggests the potential for vitamin D evaluation to improve patient prognosis following a hemorrhage.