Vitamin D and Sjögren’s Disease: Revealing the Connections—A Systematic Review and Meta-Analysis

Background: The aim of the present review was to summarize the current evidence about the impact of vitamin D deficiency on pathology and clinical manifestations of Sjögren’s disease (SD). Methods: Databases PubMed, Web of Science, Scopus, and Cochrane library were searched for studies assessing the levels of vitamin D in SD patients using the following keywords: (vitamin D OR calciferol OR cholecalciferol OR 25-hydroxyvitamin D OR 25-hydroxycholecalciferol OR calcidiol OR calcitriol OR 1,25-dihydroxycholecalciferol) AND (Sjögren’s Syndrome OR Sjögren’s disease) accessed on 20 September 2022. Out of 248 retrieved studies, following the systematic review methodology and defined inclusion and exclusion criteria, 9 clinical studies were eligible to be included in the present review: 4 of them case-control, 4 cross-sectional, and 1 cohort study. Results: Nine studies totaling 670 SD patients and 857 healthy controls were eligible for meta-analysis with moderate to high methodological quality as determined by the Newcastle–Ottawa Quality Scale (NOS). According to the obtained results, a high prevalence of hypovitaminosis D was observed in SD patients when compared to healthy controls (95% CI −10.43, −2.39; p < 0.01). Conclusion: Available evidence points to lower levels of vitamin D in patients with SD in comparison to healthy controls. However, further studies are necessary to understand the underlying mechanisms associated with the role of vitamin D in the development and disease severity of SD.