Low 25‐hydroxyvitamin D levels are associated with vitiligo: a systematic review and meta‐analysis

BACKGROUND: Vitamin D deficiency is associated with a number of autoimmune diseases. We completed a meta-analysis of observational studies to establish whether there was a relationship between hypovitaminosis D and the autoimmune skin disease vitiligo. METHODS: Comprehensive search was applied in the MEDLINE and EMBASE databases from their inception to December 2015. Inclusion criteria were observational studies that assessed 25-hydroxyvitamin D (25(OH)D) levels in adults with vitiligo. The main outcome was the mean difference in serum 25(OH)D level between patients with vitiligo and controls. RESULTS: Our search strategy identified 383 articles; seventeen studies met the criteria for full-length review and seven studies, containing the data of 1200 patients, were included in a random-effects model meta-analysis. The pooled mean difference in serum 25-hydroxyvitamin D concentration between patients with vitiligo and controls was -7.45 ng/ml (95% confidence interval, -12.99 to -1.91, P-value = 0.01). The between-study heterogeneity (I(2) ) was 96%, P = value<0.001. CONCLUSIONS: This meta-analysis identifies a significant relationship between low 25-hydroxyvitamin D levels and vitiligo, but does not prove causation. Our findings emphasize the importance of measuring 25-hydroxyvitamin D levels in patients with vitiligo. Further studies will be needed to establish whether vitamin D supplementation in this population improves the outcome of vitiligo.