Assessing the role of vitamin D in the prevention and management of chronic rhinosinusitis: a systematic review and meta-analysis.

BACKGROUND: Chronic rhinosinusitis (CRS) is a prevalent inflammatory disorder that significantly impairs quality of life. Emerging evidence suggests that vitamin D plays an immunomodulatory role in sinonasal inflammation; however, its clinical significance in CRS remains unclear. OBJECTIVE: To systematically evaluate the association between vitamin D and CRS and to assess the effects of vitamin D supplementation on disease severity, recurrence, quality of life, inflammatory markers, and postoperative outcomes. METHODS: A systematic review and meta-analysis were conducted in accordance with PRISMA guidelines. A comprehensive search of PubMed, MEDLINE, Embase, and Web of Science was performed with predefined inclusion criteria registered in PROSPERO (CRD420251001899). Eligible studies included randomized controlled trials, cohort, case-control, and cross-sectional studies assessing vitamin D levels or supplementation in adults with CRS. Data were synthesized narratively, and meta-analyses were performed using a random-effects model. Methodological quality was assessed using the Newcastle-Ottawa Scale and Cochrane Risk of Bias 2 tool. RESULTS: Twelve studies comprising 1,236 participants were included. CRS patients exhibited significantly lower vitamin D levels than controls, with deficiency rates exceeding 90% among patients with nasal polyps. Lower vitamin D levels were consistently associated with increased disease severity, including worse radiological, endoscopic, and patient-reported outcomes. Vitamin D supplementation demonstrated improvements in symptom severity, quality of life, and radiological scores, and was associated with a substantial reduction in postoperative recurrence (24.1% vs. 51.6%). Meta-analysis confirmed significantly lower serum vitamin D levels in CRS patients (MD = -12.09 ng/mL; 95% CI: -23.07 to -1.12) and a significant inverse correlation with disease severity (r = -0.52; 95% CI: -0.66 to -0.34). No statistically significant difference was observed in pooled SNOT-22 outcomes. Supplementation was well tolerated with no significant adverse effects reported. CONCLUSION: Vitamin D deficiency is strongly associated with increased disease severity and recurrence in CRS. Supplementation appears to provide clinical benefits and may serve as a promising adjunct to standard therapy. Further high-quality randomized controlled trials are required to establish optimal dosing strategies and inform clinical guideline recommendations. SYSTEMATIC REVIEW REGISTRATION: https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=1001899, identifier CRD420251001899.