Hypovitaminosis D is Associated with Psoriasis: A Systematic Review and Meta-Analysis

INTRODUCTION: Psoriasis is a chronic inflammatory and immune-mediated skin disease that affects over 7.2 million U.S. adults. Current treatment has improved clinical outcomes. Vitamin D is believed to affect the proliferation and regeneration of keratinocytes; therefore, its deficiency is a possible risk factor; however, there is still no definite evidence. The objective of this study was to synthesize existing data on the relationship between hypovitaminosis D and psoriasis. METHODS: A meta-analysis of relevant studies was conducted by doing a comprehensive search in the MEDLINE, EMBASE, and the Cochrane Central Register through July 2018 to identify relevant cohort studies and to assess serum 25-hydroxyvitamin D (25(OH)D) levels in adults with psoriasis. The primary outcome was the mean difference in serum 25(OH)D level between psoriatic patients and controls. RESULTS: The initial search identified 107 articles. Only ten studies met the criteria for full-paper review. Meta-analysis was conducted from ten prospective cohort studies involving 6,217 controls and 693 cases. The pooled mean difference in serum 25(OH)D level between psoriatic patients and controls was −6.13 ng/ml (95% CI, −10.93 to −1.32, p-value = 0.01). The between-study heterogeneity (I(2)) was 98%, p < 0.00001. CONCLUSION: Our meta-analysis was the first study to establish the relation between vitamin D and psoriasis. The result found a significant relationship between low 25(OH) D levels and psoriasis, but did not establish a causal relationship. Further studies will be required to establish whether vitamin D supplementation benefits patients with psoriasis.