Effect of vitamin B12 on the symptom severity and psychological profile of fibromyalgia patients; a prospective pre-post study

Background: Fibromyalgia (FM) as a prototypical nociplastic pain condition displays a difficult therapeutic situation in many cases. Given the promising data on the effect of vitamin B12 in improving pain and cognitive functions in various nociplastic pain conditions, we aimed to determine the efficacy of 1000 mcg daily dose of oral vitamin B12 on the symptom severity and psychological profile of FM patients.

Methods: This open-label, pre-post study was performed on FM patients whose diagnoses were confirmed by a rheumatologist based on the 2016 American College of Rheumatology (ACR). Patients were instructed to take a daily dose of 1000mcg vitamin B12 for fifty days. Outcome measures including the Revised Fibromyalgia Impact Questionnaire (FIQR), Hospital Anxiety and Depression Scale (HADS), 12-item Short-Form health survey (SF-12), and pain Visual Analog Scale (pain-VAS) were fulfilled by patients before and after the treatment.

Results: Of 30 eligible patients, 28 patients completed the study protocol. Patients were female with a mean age of 47.50 ± 8.47 years. FIQR scores in all domains improved significantly after treatment (total FIQR: 49.8 ± 21.86 vs 40.00 ± 18.36, p value < 0.01; function: 13.17 ± 7.33 vs 10.30 ± 5.84, p value: 0.01; overall: 10.32 ± 6.22 vs 8.25 ± 6.22, p value: 0.03; symptoms: 26.30 ± 10.39 vs 21.44 ± 8.58, p value < 0.01). Vitamin B12 also improved anxiety scores from 9.33 ± 4.30 to 7.70 ± 3.60, p value: 0.01. Depression, pain-VAS, and SF-12 didn't improve following the treatment. The Generalized estimating equations (GEE) analysis showed the improvement in total FIQR score is not cofounded by the improvement of anxiety and patients' baseline characteristics.

Conclusions: This study showed a short course of sublingual vitamin B12, 1000 mcg daily, significantly improves the severity of FM and anxiety score. We postulate that vitamin B12 has a strong potential to consider, at least, as adjunctive therapy of FM.

Trial registration: The study protocol was approved by the ethics committee of Guilan University of Medical Sciences (IR.GUMS.REC.1400.197) in accordance with the World Medical Association's code of ethics (Declaration of Helsinki, revised in Brazil 2013), and registered at an ICMJE and WHO recognized registry of clinical trials ( www.irct.ir ) on 28/08/2021 (registration number: IRCT20200920048782N1).