title: Vitamin D level in rheumatoid arthritis and its correlation with the disease activity: a meta-analysis.
abstract: OBJECTIVE
  This study aimed to evaluate the relationship between the 25-hydroxyvitamin D [25(OH)D] level and rheumatoid arthritis (RA) and the correlation between serum vitamin D level and RA activity.
  
  
  METHODS
  We searched the PUBMED, EMBASE, and Cochrane databases and performed a meta-analysis examining the vitamin D level and prevalence of vitamin D deficiency in patients with RA compared to healthy controls and the correlation coefficients between the vitamin D level and disease activity score 28 (DAS28) in RA patients.
  
  
  RESULTS
  Fifteen studies that included a total of 1,143 RA patients and 963 controls were available for this meta-analysis. The meta-analysis showed that the serum vitamin D level in the RA group was significantly lower than that in the control group (SMD=-0.608, 95% CI=-1.105-[-0.017], p=0.017). In addition, the prevalence of vitamin D deficiency was significantly higher in the RA group than in the control group (55.2% vs. 33.2%; OR = 2.460, 95% CI = 1.135-5.332, p=0.023). Thirteen studies evaluated the correlation between the vitamin D level and its activity in 924 RA patients. Meta-analysis showed a significant inverse correlation between the vitamin D level and DAS28 (Correlation coefficient =-0.278, 95% CI =-0.393-[-0.153], p=1.8 x 10-5).
  
  
  CONCLUSIONS
  Our meta-analysis demonstrates that serum vitamin D level is significantly low in patients with RA, vitamin D deficiency is prevalent in RA patients compared to controls, and the vitamin D level correlates inversely with RA activity. Our meta-analysis suggests that the vitamin D level is associated with susceptibility to RA and RA activity.
authors.affiliation: Division of Rheumatology, Department of Internal Medicine, Korea University College of Medicine, Seoul, Korea. lyhcgh@korea.ac.kr.
authors.forename: Young Ho
authors.initials: YH
authors.lastname: Lee
authors.affiliation: Department of Rheumatology, Hanyang University Hospital for Rheumatic Diseases, Seoul, Korea.
authors.forename: Sang-Cheol
authors.initials: SC
authors.lastname: Bae
mesh_terms: D000328:Adult; D000368:Aged; D001172:Arthritis, Rheumatoid / Q000097:blood / Q000175:diagnosis / Q000453:epidemiology*; D015415:Biomarkers / Q000097:blood; D016022:Case-Control Studies; D004198:Disease Susceptibility; D006801:Humans; D008875:Middle Aged; D016017:Odds Ratio; D015995:Prevalence; D012307:Risk Factors; D012720:Severity of Illness Index; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood; D014808:Vitamin D Deficiency / Q000097:blood / Q000175:diagnosis / Q000453:epidemiology*
chemical_list: D015415:Biomarkers; D014807:Vitamin D; C104450:25-hydroxyvitamin D