Prevalence, determinants and clinical correlates of vitamin D deficiency in adults with inhaled corticosteroid-treated asthma in London, UK

J Steroid Biochem Mol Biol. 2018 Jan;175:88-96. doi: 10.1016/j.jsbmb.2016.11.004. Epub 2016 Nov 5.

Abstract

Vitamin D deficiency is common in children with asthma, and it associates with poor asthma control, reduced forced expiratory volume in one second (FEV1) and increased requirement for inhaled corticosteroids (ICS). Cross-sectional studies investigating the prevalence, determinants and clinical correlates of vitamin D deficiency in adults with asthma are lacking. We conducted a multi-centre cross-sectional study in 297 adults with a medical record diagnosis of ICS-treated asthma living in London, UK. Details of potential environmental determinants of vitamin D status, asthma control and medication use were collected by questionnaire; blood samples were taken for analysis of serum 25(OH)D concentration and DNA extraction, and participants underwent measurement of weight, height and fractional exhaled nitric oxide concentration (FeNO), spirometry and sputum induction for determination of lower airway eosinophil counts (n=35 sub-group). Thirty-five single nucleotide polymorphisms (SNP) in 11 vitamin D pathway genes (DBP, DHCR7, RXRA, CYP2R1, CYP27B1, CYP24A1, CYP3A4 CYP27A1, LRP2, CUBN, VDR) were typed using Taqman allelic discrimination assays. Linear regression was used to identify environmental and genetic factors independently associated with serum 25(OH)D concentration, and to determine whether vitamin D status was independently associated with Asthma Control Test (ACT) score, ICS dose, FeNO, forced vital capacity (FVC), FEV1 or lower airway eosinophilia. Mean serum 25(OH)D concentration was 50.6nmol/L (SD 24.9); 162/297 (54.5%) participants were vitamin D deficient (serum 25(OH)D concentration <50nmol/L). Lower vitamin D status was associated with higher body mass index (P=0.014), non-White ethnicity (P=0.036), unemployment (P for trend=0.012), lack of vitamin D supplement use (P<0.001), sampling in Winter or Spring (P for trend <0.001) and lack of a recent sunny holiday abroad (P=0.030), but not with potential genetic determinants. Vitamin D status was not found to associate with any marker of asthma control investigated. Vitamin D deficiency is common among UK adults with ICS-treated asthma, and classical environmental determinants of serum 25(OH)D operate in this population. However, in contrast to studies conducted in children, we found no association between vitamin D status and markers of asthma severity or control.

Keywords: Asthma; Cross-sectional; Environmental; Genetics; Phenotype; Vitamin D.

Publication types

  • Multicenter Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Administration, Inhalation
  • Adolescent
  • Adrenal Cortex Hormones / therapeutic use
  • Adult
  • Aged
  • Anti-Asthmatic Agents / therapeutic use
  • Asthma / blood
  • Asthma / complications
  • Asthma / drug therapy
  • Asthma / epidemiology*
  • Body Mass Index
  • Continental Population Groups
  • Cross-Sectional Studies
  • Cytochrome P-450 Enzyme System / blood
  • Cytochrome P-450 Enzyme System / genetics
  • DNA-Binding Proteins / blood
  • DNA-Binding Proteins / genetics
  • Eosinophils / metabolism
  • Eosinophils / pathology
  • Female
  • Gene Expression Regulation
  • Humans
  • London / epidemiology
  • Low Density Lipoprotein Receptor-Related Protein-2 / blood
  • Low Density Lipoprotein Receptor-Related Protein-2 / genetics
  • Male
  • Middle Aged
  • Oxidoreductases Acting on CH-CH Group Donors / blood
  • Oxidoreductases Acting on CH-CH Group Donors / genetics
  • Receptors, Calcitriol / blood
  • Receptors, Calcitriol / genetics
  • Receptors, Cell Surface / blood
  • Receptors, Cell Surface / genetics
  • Respiratory Function Tests
  • Severity of Illness Index
  • Transcription Factors / blood
  • Transcription Factors / genetics
  • Vitamin D / analogs & derivatives*
  • Vitamin D / blood
  • Vitamin D Deficiency / blood
  • Vitamin D Deficiency / complications
  • Vitamin D Deficiency / drug therapy
  • Vitamin D Deficiency / epidemiology*

Substances

  • Adrenal Cortex Hormones
  • Anti-Asthmatic Agents
  • DBP protein, human
  • DNA-Binding Proteins
  • LRP2 protein, human
  • Low Density Lipoprotein Receptor-Related Protein-2
  • Receptors, Calcitriol
  • Receptors, Cell Surface
  • Transcription Factors
  • VDR protein, human
  • intrinsic factor-cobalamin receptor
  • Vitamin D
  • Cytochrome P-450 Enzyme System
  • 25-hydroxyvitamin D
  • Oxidoreductases Acting on CH-CH Group Donors
  • 7-dehydrocholesterol reductase