Association between serum vitamin D levels and neuropathic pain in rheumatoid arthritis patients: A cross-sectional study

Aim: Recent literature suggests that neuropathic pain (NP) and vitamin D deficiency can occur concurrently in patients with rheumatoid arthritis (RA). This study aimed to examine the development of NP in patients with RA and the relationship between NP and vitamin D. Methods: We used the Leeds Assessment of Neuropathic Symptoms and Signs (LANSS) questionnaire to evaluate NP in 93 patients with RA. Demographic and clinical data were obtained from patient files and interviews, and patients' serum vitamin D levels were recorded. Patients were requested to complete both the Short Form-36 survey and the Health Assessment Questionnaire. Results: Seventy-five of the eligible patients were female (80.6%), and 31 (33.3%) were diagnosed with NP according to the LANSS. There was a negative correlation between vitamin D levels and the LANSS score (P = 0.001). The prevalence of NP was 5.8 times higher among patients with serum vitamin D levels below 20 ng/mL than in patients with vitamin D levels >= 30 ng/mL. Based on the area under curve (AUC) values, we found that serum levels of vitamin D were a good predictor of NP diagnoses in patients with RA (AUC = 0.71). Conclusion: We found that vitamin D deficiency was asssociated with increased NP in patients with RA. Although further research is needed to clarify the association between serum vitamin D levels and NP, our study raises awareness of the need to screen for vitamin D deficiency in RA patients with NP.