Vitamin D Levels in Chronic Rhinosinusitis in Patients With or Without Nasal Polyposis: A Systematic Review.

Chronic rhinosinusitis (CRS) is a large group of heterogeneous diseases characterized by extensive inflammation of the nasal mucosa and sinuses. Vitamin D (VD), as an immunoregulatory hormone, may play an important role in the pathophysiology of CRS. The purpose of this study is to review the existing literature that correlates VD levels with CRS with or without nasal polyps. A systematic manual search was conducted in the PubMed and Google Scholar databases up to July 2023. Articles from PubMed and the first 100 articles from Google Scholar were recorded for our research. Keywords used were the following: vitamin D, chronic rhinosinusitis, and nasal polyps. Among the 134 articles retrieved, only 18 were eligible. The other 116 studies were excluded as they related VD levels with other conditions (e.g., allergic rhinitis) and for other reasons. However, we identified two more eligible records through the manual research of the above-mentioned 132 studies, and finally, 20 records were included in the current review. The review concerned case-control studies, prospective, retrospective, and cross-sectional studies. Based on our review, we concluded that CRS patients are correlated with the lowest VD levels, accompanied by increased severity of the disease, especially in those with nasal polyposis. Patients can benefit from appropriate VD supplementation, and serum VD levels should be included in the laboratory assessment of CRS. However, due to the heterogeneity of the individuals involved, more well-designed clinical trials as well as randomized clinical trials should be conducted for further validation of the above findings in the general population in the future.