Vitamin D levels in allergic rhinitis: a systematic review and meta-analysis

Background: We aimed to systematically review observational studies investigating the relationship between vitamin D levels and allergic rhinitis (AR). Methods: Studies were selected if they evaluated the relationship between vitamin D levels and AR, and included studies that evaluated other allergic conditions if those studies also contained data on AR. We assessed the incidence and prevalence of AR according to vitamin D levels and compared vitamin D levels in patients with AR to levels in controls. Results: Nineteen studies were selected. Of these, only seven focused solely on AR; 10 studies evaluated the other allergic diseases as well as AR; and two studies evaluated asthma primarily, but also included data on patients with AR. The pooled odds ratios (ORs) for the incidence of AR according to vitamin D levels were not statistically significant for either children or adults. Lower vitamin D levels were associated with a higher AR prevalence only in children (pooled OR [95% confidence interval (CI)], 0.75 [0.58, 0.98]). The pooled mean vitamin D level in patients with AR was lower than that of controls only in children (pooled means difference [95% CI], −7.63 [−13.08, −2.18]). Conclusions: Prior vitamin D levels were not related to developing AR, but lower vitamin D levels were associated with a higher AR prevalence only in children. There is insufficient evidence to support vitamin D supplementation for AR prevention. However, physicians should consider evaluating patients for vitamin D deficiency during AR management, especially in children.