title: Vitamin D levels and risk of acute exacerbations of chronic obstructive pulmonary disease: a prospective cohort study.
abstract: BACKGROUND
  Low blood levels of 25-hydroxyvitamin D (25[OH]D) have been associated with a higher risk of respiratory infections in general populations and higher risk of exacerbations of lung disease in people with asthma. We hypothesized that low blood levels of 25(OH)D in patients with chronic obstructive pulmonary disease (COPD) would be associated with an increased risk of acute exacerbations of COPD (AECOPD).
  
  
  OBJECTIVE
  To determine if baseline 25(OH)D levels relate to subsequent AECOPD in a cohort of patients at high risk for AECOPD.
  
  
  METHODS
  Plasma 25(OH)D was measured at baseline in 973 participants on entry to a 1-year study designed to determine if daily azithromycin decreased the incidence of AECOPD. Relationships between baseline 25(OH)D and AECOPD over 1 year were analyzed with time to first AECOPD as the primary outcome and exacerbation rate as the secondary outcome.
  
  
  RESULTS
  In this largely white (85%) sample of North American patients with severe COPD (mean FEV(1) 1.12L; 40% of predicted), mean 25(OH)D was 25.7 ± 12.8 ng/ml. A total of 33.1% of participants were vitamin D insufficient (≥20 ng/ml but <30 ng/ml); 32% were vitamin D deficient (<20 ng/ml); and 8.4% had severe vitamin D deficiency (<10 ng/ml). Baseline 25(OH)D levels had no relationship to time to first AECOPD or AECOPD rates.
  
  
  CONCLUSIONS
  In patients with severe COPD, baseline 25(OH)D levels are not predictive of subsequent AECOPD. Clinical trial registered with www.clinicaltrials.gov (NCT00119860).
authors.affiliation: Pulmonary Section, Minneapolis Veterans Affairs Medical Center, Minnesota 55417, USA. kunis001@umn.edu
authors.forename: Ken M
authors.initials: KM
authors.lastname: Kunisaki
authors.forename: Dennis E
authors.initials: DE
authors.lastname: Niewoehner
authors.forename: John E
authors.initials: JE
authors.lastname: Connett
mesh_terms: D000208:Acute Disease; D000368:Aged; D000900:Anti-Bacterial Agents / Q000627:therapeutic use; D017963:Azithromycin / Q000627:therapeutic use; D015415:Biomarkers / Q000097:blood; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016016:Proportional Hazards Models; D011446:Prospective Studies; D029424:Pulmonary Disease, Chronic Obstructive / Q000097:blood / Q000188:drug therapy / Q000209:etiology*; D012008:Recurrence; D012306:Risk; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood; D014808:Vitamin D Deficiency / Q000097:blood / Q000150:complications*
chemical_list: D000900:Anti-Bacterial Agents; D015415:Biomarkers; D014807:Vitamin D; D017963:Azithromycin; C104450:25-hydroxyvitamin D
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