Abstract
BACKGROUND: In this systematic review and meta-analysis, we aimed to investigate the relationship between vitamin D levels and brain volumetric changes in human studies. METHOD: We conducted a comprehensive search in PubMed, Scopus, and Google Scholar databases up to December 2024. A total of 450 studies were identified. Following title, abstract, and full-text screening, we included three studies for analysis. Data were extracted from these studies and analyzed using appropriate statistical methods. RESULT: Our analysis revealed that the included case-control and cohort studies were conducted in the United States, Norway, and the Netherlands. The studies exhibited a range of characteristics, including sample size (number of patients: 183-240), demographic variables, and methods of assessing both vitamin D levels and brain volume. Brain volume assessments included gray matter, white matter, and total brain volume. The total follow-up duration across studies was 11 years. The age of participants ranged from 30 to 64 years in one study, while in another, they were aged 65 years or older. The meta-analysis indicated no significant association between vitamin D levels and brain volumetric changes across the included studies (effect size: 0.07, 95 % CI= [-0.01, 0.15], P = 0.07, I(2)=54.44 %). CONCLUSION: This meta-analysis did not establish a significant association between vitamin D levels and brain volumetric changes. These findings highlighted the need for further large-scale studies to clarify the potential role of vitamin D in brain volume and to better understand the underlying mechanisms involved.