Vitamin D Status and Supplementation in Chronic Rhinosinusitis: A Systematic Review and Meta‐Analysis

OBJECTIVES: To investigate the relationship between vitamin D (VD) levels and chronic rhinosinusitis (CRS), and to evaluate the therapeutic efficacy of VD supplementation for CRS. DATA SOURCES: Two independent reviewers systematically searched PubMed, Embase, and the Cochrane Library to identify studies that assessed the association between CRS and VD, as well as the therapeutic effects of VD supplementation on CRS outcomes. REVIEW METHODS: Meta-analyses were conducted to compare VD levels between CRS patients and controls and to evaluate the efficacy of VD supplementation. Random- or fixed-effects models were applied as appropriate. Sensitivity and subgroup analyses were performed to investigate potential sources of heterogeneity. RESULTS: A pooled analysis of 15 studies showed significantly lower serum VD levels in CRS patients compared to controls (SMD = -0.98; P < .001). Both 25(OH)D3 and 25(OH)D assays showed lower VD levels in CRS patients (SMD = -1.24, P < .001 vs SMD = -0.77, P < .001). Subgroup analyses also revealed consistent reductions in both CRS with nasal polyps (CRSwNP; SMD = -1.05; P < .001) and CRS without nasal polyps (CRSsNP; SMD = -1.02; P < .001). Moreover, four randomized controlled trials indicated that VD supplementation significantly improved Sino-Nasal Outcome Test-22 (SNOT-22) scores at