title: Association between vitamin D status and COPD phenotypes.
abstract: BACKGROUND
  It has been suggested that identifying phenotypes in chronic obstructive pulmonary disease (COPD) might improve treatment outcome and the accuracy of prediction of prognosis. In observational studies vitamin D deficiency has been associated with decreased pulmonary function, presence of emphysema and osteoporosis, upper respiratory tract infections, and systemic inflammation. This could indicate a relationship between vitamin D status and COPD phenotypes. The aim of this study was to assess the association between vitamin D levels and COPD phenotypes. In addition, seasonality of vitamin D levels was examined.
  
  
  METHODS
  A total of 91 patients from a Danish subpopulation of the "Evaluation of COPD Longitudinally to Identify Predictive Surrogate End-points" cohort took part in a biomarker substudy. Vitamin D concentration was measured from blood samples taken at two visits, approximately 6 months apart. The participants were 40-75-year-old patients with COPD and had a smoking history of >10 pack-years.
  
  
  RESULTS
  Fifty-six patients had 25-hydroxyvitamin D measured from blood samples from both visits. In the final model of the multivariate analyses, the factors that were associated with vitamin D deficiency at the first visit were age (OR: 0.89, p = 0.02) and summer season (OR: 3.3, p = 0.03). Factors associated with vitamin D level also at the first visit were age (B: 0.9, p = 0.02) and 6 min walking distance (B: 0.05, p = 0.01).
  
  
  CONCLUSIONS
  Vitamin D was not associated with COPD phenotypes and season did not seem to be a determinant of vitamin D levels in patients with moderate to severe COPD.
authors.affiliation: Section of Respiratory Medicine, Hvidovre University Hospital, Kettegaard Allé 30, 2650, Hvidovre, Denmark, miamoberg@hotmail.com.
authors.forename: Mia
authors.initials: M
authors.lastname: Moberg
authors.forename: Thomas
authors.initials: T
authors.lastname: Ringbaek
authors.forename: Nassim Bazeghi
authors.initials: NB
authors.lastname: Roberts
authors.forename: Jørgen
authors.initials: J
authors.lastname: Vestbo
mesh_terms: D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000097:blood; D003718:Denmark; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D016014:Linear Models; D016015:Logistic Models; D008137:Longitudinal Studies; D008168:Lung / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D016017:Odds Ratio; D010641:Phenotype; D029424:Pulmonary Disease, Chronic Obstructive / Q000097:blood* / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology; D012307:Risk Factors; D012621:Seasons; D012720:Severity of Illness Index; D012907:Smoking / Q000009:adverse effects; D013997:Time Factors; D014797:Vital Capacity; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood
chemical_list: D015415:Biomarkers; D014807:Vitamin D; C104450:25-hydroxyvitamin D
references.citation: N Engl J Med. 2010 Sep 16;363(12):1128-38
references.pmid: 20843247
references.citation: Joint Bone Spine. 2010 Dec;77(6):552-7
references.pmid: 21067953
references.citation: Cancer Epidemiol Biomarkers Prev. 2011 Apr;20(4):585-90
references.pmid: 21454423
references.citation: Chest. 2005 Dec;128(6):3792-8
references.pmid: 16354847
references.citation: Respir Med. 2013 Oct;107(10):1578-88
references.pmid: 23809536
references.citation: Am J Respir Crit Care Med. 2010 Sep 1;182(5):598-604
references.pmid: 20522794
references.citation: Respir Med. 2011 Sep;105(9):1338-44
references.pmid: 21530214
references.citation: Eur Respir J. 2008 Apr;31(4):869-73
references.pmid: 18216052
references.citation: PLoS One. 2012;7(6):e38934
references.pmid: 22737223
references.citation: Eur Respir J. 2013 Feb;41(2):309-16
references.pmid: 22556020
references.citation: Chest. 2002 Feb;121(2):609-20
references.pmid: 11834678
references.citation: Age Ageing. 2013 May;42(3):404-8
references.pmid: 23542723
references.citation: Am J Clin Nutr. 2008 Dec;88(6):1519-27
references.pmid: 19064511
references.citation: Arch Intern Med. 2009 Feb 23;169(4):384-90
references.pmid: 19237723
references.citation: Ann Intern Med. 2012 Jan 17;156(2):105-14
references.pmid: 22250141
references.citation: Am J Respir Crit Care Med. 2013 Feb 15;187(4):347-65
references.pmid: 22878278
references.citation: Int J Chron Obstruct Pulmon Dis. 2013;8:97-104
references.pmid: 23430315
references.citation: Thorax. 2010 Mar;65(3):215-20
references.pmid: 19996341
references.citation: PLoS One. 2013;8(1):e53670
references.pmid: 23341971