title: Is Serum Hypovitaminosis D Associated with Chronic Widespread Pain Including Fibromyalgia? A Meta-analysis of Observational Studies.
abstract: BACKGROUND
  Chronic widespread pain (CWP) is a global musculoskeletal disorder leading to disability and a reduced quality of life. Low levels of serum vitamin D has long been proposed to be associated with CWP, but previous research remains inconclusive.
  
  
  OBJECTIVE
  To determine whether hypovitaminosis D was independently associated with CWP.
  
  
  METHODS
  Meta-analysis of observational study.
  
  
  METHODS
  Electronic databases were searched for studies published up to November 2014 comparing the prevalence of hypovitaminosis D and serum vitamin D levels between participants with and without CWP. The crude and adjusted odds ratios (ORs) of hypovitaminosis D with CWP were calculated. Subgroup analysis according to gender, threshold of hypovitaminosis, and definition of patients was performed, as well as meta-regression to test the linear relationship between crude ORs and the latitude of study locations.
  
  
  RESULTS
  Twelve studies were included, comprising 1,854 patients with CWP. The patient group showed a significantly higher risk of hypovitaminosis D than the control group (crude OR, 1.63; 95% CI, 1.20-2.23). The association was slightly attenuated after adjusting confounders, with a pooled adjusted OR of 1.41 (95% CI, 1.00-2.00). There was an increase in ORs of hypovitaminosis D using a lower diagnostic value of serum vitamin D (8 and 10 ng/mL). The subgroup analysis according to gender and definition of CWP did not reveal significant between-group differences. The meta-regression showed no linear relationship between latitude and the crude ORs.
  
  
  CONCLUSIONS
  There was a positive crude association between hypovitaminosis D and CWP, and the association was likely to remain after adjusting confounding factors. Use of a cut-off value of hypovitaminosis D (8-10 ng/mL) could better define the population with and without CWP. Further prospective follow-up studies are warranted to clarify the causal relationship between hypovitaminosis D and CWP.
authors.affiliation: Department of Physical Medicine and Rehabilitation, National Taiwan University Hospital, Bei-Hu Branch and National Taiwan University College of Medicine;
authors.forename: Ming-Yen
authors.initials: MY
authors.lastname: Hsiao
authors.affiliation: Department of Physical Medicine and Rehabilitation, National Taiwan University Hospital, Chu-Tung Branch;
authors.forename: Chen-Yu
authors.initials: CY
authors.lastname: Hung
authors.affiliation: Department of Physical Medicine and Rehabilitation, National Taiwan University Hospital, Bei-Hu Branch and National Taiwan University College of Medicine;
authors.forename: Ke-Vin
authors.initials: KV
authors.lastname: Chang
authors.affiliation: Department of Physical Medicine and Rehabilitation, National Taiwan University Hospital, Bei-Hu Branch and National Taiwan University College of Medicine;
authors.forename: Der-Sheng
authors.initials: DS
authors.lastname: Han
authors.affiliation: Department of Physical Medicine and Rehabilitation, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan.
authors.forename: Tyng-Guey
authors.initials: TG
authors.lastname: Wang
mesh_terms: D059350:Chronic Pain / Q000150:complications* / Q000453:epidemiology; D005356:Fibromyalgia / Q000150:complications* / Q000453:epidemiology; D006801:Humans; D064887:Observational Studies as Topic; D015995:Prevalence; D014808:Vitamin D Deficiency / Q000097:blood* / Q000150:complications* / Q000453:epidemiology