title: Serum 25-hydroxyvitamin D levels and peripheral neuropathy in patients with type 2 diabetes: a systematic review and meta-analysis.
abstract: BACKGROUND
  Vitamin D is a multifunctional pro-hormone and has widespread actions in human body. Several studies showed a possible association between vitamin D deficiency and diabetic peripheral neuropathy (DPN) in patients with type 2 diabetes, but no definite conclusion was available.
  
  
  METHODS
  A systematic review and meta-analysis was performed to comprehensively assess the association between serum 25-hydroxyvitamin D [25(OH)D] levels and DPN in patients with type 2 diabetes. Data from eligible studies were pooled using meta-analysis.
  
  
  RESULTS
  Six studies that involved a total of 1,484 type 2 diabetic patients were finally included into the meta-analysis. Meta-analysis showed that there were obviously decreased serum 25(OH)D levels in DPN patients [weighted mean difference (WMD) = -6.36 ng/ml, 95 % confidence interval (95 % CI) -8.57 to -4.14, P < 0.00001]. Vitamin D deficiency was also significantly associated with increased risk of DPN in patients with type 2 diabetes [odds ratio (OR) 2.88, 95 % CI 1.84-4.50, P < 0.00001]. Meta-analysis of three studies with adjusted estimates showed that vitamin D deficiency was independently associated with increased risk of DPN in patients with type 2 diabetes (OR 2.68, 95 % CI 1.67-4.30, P < 0.0001). Sensitivity analysis showed that there was no obvious change in the pooled estimates.
  
  
  CONCLUSIONS
  Vitamin D is involved in the development of DPN in type 2 diabetic patients, and vitamin D deficiency is very likely to be associated with DPN in type 2 diabetic patients. Further studies are needed to validate the association between vitamin D deficiency and DPN.
authors.affiliation: Department of Endocrinology, Affiliated Hospital of Qingdao University, 16 Jiangsu Road, Qingdao, 266003, China.
authors.forename: W S
authors.initials: WS
authors.lastname: Lv
authors.affiliation: Department of Endocrinology, Affiliated Hospital of Qingdao University, 16 Jiangsu Road, Qingdao, 266003, China.
authors.forename: W J
authors.initials: WJ
authors.lastname: Zhao
authors.affiliation: Department of Endocrinology, Affiliated Hospital of Qingdao University, 16 Jiangsu Road, Qingdao, 266003, China.
authors.forename: S L
authors.initials: SL
authors.lastname: Gong
authors.affiliation: Department of Endocrinology, Affiliated Hospital of Qingdao University, 16 Jiangsu Road, Qingdao, 266003, China.
authors.forename: D D
authors.initials: DD
authors.lastname: Fang
authors.affiliation: Department of Endocrinology, Affiliated Hospital of Qingdao University, 16 Jiangsu Road, Qingdao, 266003, China. robin.wangqy@gmail.com.|Essencemed Clinic, Weifang, 261000, China. robin.wangqy@gmail.com.
authors.forename: B
authors.initials: B
authors.lastname: Wang
authors.affiliation: Department of Endocrinology, Affiliated Hospital of Qingdao University, 16 Jiangsu Road, Qingdao, 266003, China.
authors.forename: Z J
authors.initials: ZJ
authors.lastname: Fu
authors.affiliation: Department of Endocrinology, Affiliated Hospital of Qingdao University, 16 Jiangsu Road, Qingdao, 266003, China.
authors.forename: S L
authors.initials: SL
authors.lastname: Yan
authors.affiliation: Department of Endocrinology, Affiliated Hospital of Qingdao University, 16 Jiangsu Road, Qingdao, 266003, China. nlwang@126.com.
authors.forename: Y G
authors.initials: YG
authors.lastname: Wang
mesh_terms: D003924:Diabetes Mellitus, Type 2 / Q000097:blood*; D003929:Diabetic Neuropathies / Q000097:blood*; D006801:Humans; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D
keywords: 25-Hydroxyvitamin D; Diabetic peripheral neuropathy; Meta-analysis