ASTHMA – comparing the impact of vitamin D versus UVR on clinical and immune parameters. Issue 3 (16th January 2017)

• Record Type: Journal Article
• Authors: Morgan, Kylie A.; Mann, Elizabeth H.; Young, Antony R.; Hawrylowicz, Catherine M.
• Is Part Of: Photochemical & photobiological sciences. Volume 16:Issue 3(2017)
• Page Start: 399
• Page End: 410
• Publication Date: 2017-01-16
• Subjects: Photochemistry -- Periodicals; Photobiology -- Periodicals; 541.35
• DOI: 10.1039/c6pp00407e
• Languages: English
• ISSNs: 1474-905X

Abstract

Abstract : Asthma is estimated to affect more than 300 million individuals worldwide. Vitamin D is increasingly believed to beneficially influence asthma incidence and control, likely due to effects on innate and adaptive immunity. The primary mechanism for increasing vitamin D in the body is via UVB radiation of skin, however whether UVB has comparable effects to vitamin D on relevant immune mechanisms and asthma is unclear. Abstract : The incidence of asthma has increased markedly since the 1960s and is currently estimated to affect more than 300 million individuals worldwide. A number of environmental factors are implicated in asthma pathogenesis, one of which is vitamin D. Vitamin D deficiency is a global health concern and has increased in parallel with asthma incidence. Epidemiological studies report associations between low vitamin D status, assessed as circulating levels of 25-hydroxyvitamin D, with asthma incidence, severity, exacerbations and responses to treatment. This has led to clinical studies to test whether increasing the levels of vitamin D improves asthma management. Despite being highly variable in dosing regimens, design and outcomes, meta-analyses suggest overall positive outcomes with respect to reduced asthma exacerbations and steroid requirements. The primary mechanism for increasing vitamin D levels in the body is through exposure of the skin to the ultraviolet B (UVB) component of ultraviolet radiation (UVR), most commonly from sun exposure. However, only a limited number of studies investigating the impact of UVR on the asthmatic response have been performed; these generally report on the impact of latitude as a surrogate of sun exposure, or address this in animal models. To the best of our knowledge no comprehensive trials to assess the impact of UVB radiation on asthma outcomes have been performed. Within this review we discuss observational and clinical studies in this field, and innate and adaptive immune mechanisms through which UVR and vitamin D may impact respiratory health, and asthma. We highlight the heterogeneity of asthmatic disease, which is likely to impact upon the efficacy of interventional studies, and briefly overview more recent findings relating to the impact of vitamin D/UVR on the development of asthma.