Vitamin D deficiency and atopic dermatitis severity in a Bangladeshi population living in East London: A cross-sectional study.

Background: Atopic eczema is a common, chronic, inflammatory skin condition with considerable heterogeneity. South Asian people living in the UK frequently have low serum vitamin D3 (25(OH)D), and those with atopic disease can present with severe eczema. The association between vitamin D deficiency and eczema severity, and the role of vitamin D supplementation in atopic eczema is inconsistent, and under-researched in people with Asian ancestry.

Objectives: This cross-sectional study investigates the association between serum 25(OH)D and eczema severity in a cohort of South Asian children and young adults living in London.

Methods: Eligible participants were Bangladeshi children and young adults aged 0-30 years with eczema, living in London and participating in the Tower Hamlets Eczema Assessment study. Data was collected via parent/patient self-reporting, clinical history and examination, and hospital databases. 25(OH)D levels were documented retrospectively, if available, from hospital databases. Eczema severity was classified by Eczema Area and Severity Index (EASI) score less than or greater than 10 (clear-mild vs. moderate-severe). Multivariate logistic regression was used to adjust for confounding factors.

Results: 681 participants were included in analyses. 25(OH)D results were available for 49.6% (338/681), 84.3% of which had deficient or insufficient lowest 25(OH)D. Lowest 25(OH)D was inversely correlated with EASI score (Spearman's rank  = -0.24,  < 0.001). 26.1% (178/681) had EASI >10 and a lower median lowest and nearest 25(OH)D. After adjustment for confounding EASI > 10 was significantly associated with a lowest 25(OH)D < 25 (OR 3.21, 95%CI 1.35, 8.60), use of mild-moderate potency topical steroid on the face and neck (OR 3.11, 95%CI 1.86, 5.31), calcineurin inhibitor on the face and neck (OR 2.79, 95% CI 1.26, 6.10) and potent - very potent topical steroid on the face and neck (OR2.23, 95%CI 1.02, 4.77) and body (OR 2.11, 95%CI 1.18, 3.87).

Discussion: Vitamin D plays a role in modulation of proteins required for skin barrier function and regulation of the innate immune system, suggesting 25(OH)D deficiency contributes to skin inflammation. This study demonstrates a relationship between 25(OH)D deficiency and worse eczema severity in a cohort of South Asian children and young adults.