Vitamin D levels do not correlate with severity of idiopathic peripheral neuropathy

Background and aims: Peripheral neuropathy (PN) is a common neurological condition in elderly adults. Vitamin D deficiency has been associated with diabetic and chemotherapy-induced neuropathy, but its role in idiopathic PN, in which no underlying cause of neuropathy can be identified, has not been investigated. Methods: Two hundred thirty patients with idiopathic PN enrolled in the Peripheral Neuropathy Research Registry (PNRR) at Johns Hopkins University School of Medicine had vitamin D testing information on record. Linear and logistic regressions were used to investigate the relationship between absolute vitamin D level or vitamin D insufficiency (<20 ng/mL) and both the severity of neuropathy as measured by the reduced total neuropathy score (TNSr) and severity of neuropathic pain. Results: Sixteen (7%) patients were vitamin D insufficient (<20 ng/mL). Controlling for factors known to correlate with severity of neuropathy, there was no correlation between absolute vitamin D levels and TNSr (correlation coefficient 0.01, 95% CI -0.03 to 0.07, p = .59) and no association between vitamin D insufficiency and TNSr (correlation coefficient 0.3, 95% CI -2.8 to 3.4, p = .86). Vitamin D insufficiency was not associated with the presence of neuropathic pain (OR 4.1, 95% CI 0.6-26.0, p = .13), and there was no correlation between vitamin D levels and pain score (correlation coefficient 0.01, 95% CI -0.02 to 0.03, p = .59). Interpretation: In a single-center cohort of patients with idiopathic PN, there was no correlation between vitamin D levels and the severity of neuropathy or neuropathic pain.