Association between vitamin D deficiency and allergic symptom in pregnant women

Background
Vitamin D has been reported to affect both innate, and acquired immunity with immune cells such as dendritic cells having the vitamin D receptors. The co-occurrence of the high prevalence of allergic diseases and vitamin D deficiency globally documented in recent decades, has prompted a hypothesis on whether there is a reasonable association between them.
Objective
To investigate the association between serum vitamin D deficiency and allergic symptoms.
Methods
Historical cohort. On a cohort study for the association between desert dust exposure and allergic symptoms in 3,327 pregnant women during spring and fall in 2011–2013 in Japan conducted as an adjunct study to the Japan Environment and Children’s Study, we promptly acquired subjects’ daily allergic symptom scores by sending a web-based questionnaire to each participant on some days. Of the 29,434 answers provided by 3,327 participating pregnant women, we extracted 13,356 answers from 1,475 pregnant women that were answered within a 3-month period after blood samplings. And we measured 25(OH)D levels on those samples to investigate the association between their vitamin D deficiency (serum 25(OH)D < 20ng/mL) and the occurrence of any allergic symptom (allergic symptom score> 0) within 3 months.
Results
Serum 25(OH)D was less than 20ng/mL in 1,233 of 1,745 samples (70.7%). The adjusted odds ratio (aOR) for occurrence of any allergic symptom in deficient cases compared with non-deficient cases was 1.33 (95% CI: 1.07–1.64, p = 0.01). Further, vitamin D deficiency significantly enhanced the risk increase at desert dust events and at pollen exposure (p-values for interaction <0.1).
Conclusion
We confirmed the association between serum vitamin D deficiency and allergic symptoms in Japanese pregnant women.