Is Serum Hypovitaminosis D Associated with Chronic Widespread Pain Including Fibromyalgia? A Meta-analysis of Observational Studies

Background: Chronic widespread pain (CWP) is a global musculoskeletal disorder leading todisability and a reduced quality of life. Low levels of serum vitamin D has long been proposedto be associated with CWP, but previous research remains inconclusive.Objectives: To determine whether hypovitaminosis D was independently associated withCWP.Study Design: Meta-analysis of observational study.Methods: Electronic databases were searched for studies published up to November 2014comparing the prevalence of hypovitaminosis D and serum vitamin D levels between participantswith and without CWP. The crude and adjusted odds ratios (ORs) of hypovitaminosis D withCWP were calculated. Subgroup analysis according to gender, threshold of hypovitaminosis,and definition of patients was performed, as well as meta-regression to test the linearrelationship between crude ORs and the latitude of study locations.Results: Twelve studies were included, comprising 1,854 patients with CWP. The patientgroup showed a significantly higher risk of hypovitaminosis D than the control group (crudeOR, 1.63; 95% CI, 1.20 – 2.23). The association was slightly attenuated after adjustingconfounders, with a pooled adjusted OR of 1.41 (95% CI, 1.00 – 2.00). There was an increasein ORs of hypovitaminosis D using a lower diagnostic value of serum vitamin D (8 and 10ng/mL). The subgroup analysis according to gender and definition of CWP did not revealsignificant between-group differences. The meta-regression showed no linear relationshipbetween 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-offvalue of hypovitaminosis D (8 – 10 ng/mL) could better define the population with and withoutCWP. Further prospective follow-up studies are warranted to clarify the causal relationshipbetween hypovitaminosis D and CWP.Key words: Vitamin D, fibromyalgia, chronic widespread pain, meta-analysis