Association between vitamin D serum levels and fibromyalgia disease activity

Fibromyalgia (FM) is a chronic musculoskeletal disorder characterized by widespread, long-term pain and multiple tender points revealed in physical examination. Previous studies about the relationship between serum vitamin D level and FM have reported paradoxical results. This cross-sectional study aimed to evaluate levels of vitamin D and its relationship with the severity of FM. Based on the American College of Rheumatology (ACS) criteria, 100 female patients with FM were enrolled in this study, and their serum vitamin D levels were screened. Vitamin D deficiency is defined as a level less than 12 ng/mL; insufficiency is defined as a level between 12–29 ng/mL; and sufficiency is a level equal to or greater than 30 ng/mL. Disease severity was evaluated by symptom severity scale (SSS) score and documented using designed questionnaires. Among the 100 female FM patients enrolled in this study, mean patient age was 35.60 years; 47% of them had vitamin D deficiency, 36% had vitamin D insufficiency, and only 17% had normal vitamin D serum levels. Vitamin D deficiency was reported among 50% of patients with an SSS score between 9 and 12, 49% of patients with an SSS score between 5 and 8, and 14.3% of patients with an SSS score between 1 and 4. There was no significant correlation between patient age and vitamin D level (p-value=0.12). Moreover, no significant correlation was found between patient age and SSS score (p-value=0.36). The current study demonstrated that there was no statistically significant relationship between FM disease activity and vitamin D serum level.