title: The association between vitamin D and COPD risk, severity, and exacerbation: an updated systematic review and meta-analysis.
abstract: BACKGROUND
  In recent years, the pleiotropic roles of vitamin D have been highlighted in various diseases. However, the association between serum vitamin D and COPD is not well studied. This updated systematic review and meta-analysis aimed to assess the relationship between vitamin D and the risk, severity, and exacerbation of COPD.
  
  
  METHODS
  A systematic literature search was conducted in PubMed, Medline, EMBASE, Chinese National Knowledge Infrastructure, Wanfang, and Weipu databases. The pooled risk estimates were standardized mean difference (SMD) with 95% confidence interval (CI) for vitamin D levels and odds ratio (OR) with 95% CI for vitamin D deficiency. Meta-regression and subgroup analyses were performed on latitude, body mass index, and assay method.
  
  
  RESULTS
  A total of 21 studies, including 4,818 COPD patients and 7,175 controls, were included. Meta-analysis showed that lower serum vitamin D levels were found in COPD patients than in controls (SMD: -0.69, 95% CI: -1.00, -0.38,P<0.001), especially in severe COPD (SMD: -0.87, 95% CI: -1.51, -0.22,P=0.001) and COPD exacerbation (SMD: -0.43, 95% CI: -0.70, -0.15,P=0.002). Vitamin D deficiency was associated with increased risk of COPD (OR: 1.77, 95% CI: 1.18, 2.64,P=0.006) and with COPD severity (OR: 2.83, 95% CI: 2.00, 4.00,P<0.001) but not with COPD exacerbation (OR: 1.17, 95% CI: 0.86, 1.59,P=0.326). Assay methods had significant influence on the heterogeneity of vitamin D deficiency and COPD risk.
  
  
  CONCLUSIONS
  Serum vitamin D levels were inversely associated with COPD risk, severity, and exacerbation. Vitamin D deficiency is associated with increased risk of COPD and severe COPD but not with COPD exacerbation. It is worth considering assay methods in the heterogeneity sources analysis of association between vitamin D deficiency and COPD.
authors: Department of Respiratory and Critical Care Medicine, West China Hospital, Sichuan University, Chengdu, Sichuan, People's Republic of China.
authors: Min
authors: M
authors: Zhu
authors: Department of Respiratory and Critical Care Medicine, West China Hospital, Sichuan University, Chengdu, Sichuan, People's Republic of China.
authors: Ting
authors: T
authors: Wang
authors: Department of Respiratory and Critical Care Medicine, West China Hospital, Sichuan University, Chengdu, Sichuan, People's Republic of China.
authors: Chengdi
authors: C
authors: Wang
authors: Department of Respiratory and Critical Care Medicine, West China Hospital, Sichuan University, Chengdu, Sichuan, People's Republic of China.
authors: Yulin
authors: Y
authors: Ji
mesh_terms: D015415:Biomarkers / Q000097:blood; D016022:Case-Control Studies; D019587:Dietary Supplements; D018450:Disease Progression; D006801:Humans; D008168:Lung / Q000503:physiopathology*; D016017:Odds Ratio; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis / Q000453:epidemiology* / Q000503:physiopathology / Q000628:therapy; D018570:Risk Assessment; D012307:Risk Factors; D012720:Severity of Illness Index; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood / Q000627:therapeutic use; D014808:Vitamin D Deficiency / Q000097:blood / Q000175:diagnosis / Q000188:drug therapy / Q000453:epidemiology*
chemical_list: D015415:Biomarkers; D014807:Vitamin D; C104450:25-hydroxyvitamin D
keywords: COPD; exacerbation; meta-analysis; risk; severity; vitamin D