Serum 25-Hydroxyvitamin D Levels and Disease Activity in Chronic Spontaneous Urticaria: A Multicentre Cross-Sectional Study from South India

Abstract

Background. Chronic spontaneous urticaria (CSU) is a mast-cell–driven disorder in which an immunomodulatory role for vitamin D has been proposed. Data from Indian populations relating serum 25-hydroxyvitamin D [25(OH)D] to an objective measure of disease activity remain limited. Objective. To examine the association between serum 25(OH)D and CSU disease activity, quantified by the seven-day Urticaria Activity Score (UAS7), and to determine whether it is independent of demographic, anthropometric and clinical covariates. Methods. In this multicentre cross-sectional study, 150 adults with CSU across six centres in underwent standardized assessment, UAS7 scoring, and measurement of serum 25(OH)D and routine inflammatory markers. Associations were tested with Pearson and Spearman correlation, one-way ANOVA with Tukey post-hoc comparison, and multivariable linear regression. Results. Mean age was 38.7 ± 11.2 years; 82 (54.7%) were women. Vitamin D deficiency (<20 ng/mL) was present in 70 (46.7%), insufficiency (20–29 ng/mL) in 62 (41.3%) and sufficiency (≥30 ng/mL) in 18 (12.0%). Serum 25(OH)D correlated inversely with UAS7 (Pearson r = –0.55; Spearman ρ = –0.52; both p < 0.001). Mean UAS7 fell stepwise across the deficient (26.2 ± 8.8), insufficient (20.6 ± 8.3) and sufficient (11.7 ± 7.0) groups (ANOVA F = 23.1, p < 0.001; all pairwise p < 0.001). In multivariable regression, each 1 ng/mL increase in 25(OH)D was independently associated with a 0.62-point lower UAS7 (95% CI –0.78 to –0.46, p < 0.001; adjusted R² = 0.31). Conclusions. Lower serum 25(OH)D was independently associated with greater CSU disease activity in this South Indian cohort, supporting assessment of vitamin D status in CSU and motivating interventional trials of supplementation.