An inverse association between serum vitamin D levels with the presence and severity of impaired nerve conduction velocity and large fiber peripheral neuropathy in diabetic subjects.

Diabetic neuropathy (DN) is the most common complication of diabetes mellitus (DM) and also the major cause of morbidity and mortality in diabetic patients. There have been recent speculations that circulating 25-hydroxyvitamin D (25(OH)-D) could be involved in DN development and progression. This study explored the association between serum 25(OH)-D and DN in diabetic subjects by performing strict matching of possible confounders. Overall, 33 diabetic subjects with DN and 29 controls matched in terms of age, sex, BMI, height and disease duration entered this study. Nerve conduction velocity (NCV) was performed to determine the existence and severity of large fiber neuropathy. 25(OH)-D had significantly lower value in DN group (21.2 ± 11.5 vs. 13.5 ± 5.1 ng/mL, P = 0.001). None of the other observed variables showed a significant association with existence and severity of DN. After adjustment for all studied variables, serum vitamin D had an independent and inverse association with both DN presence and severity, as each 1 ng/mL increase in serum 25(OH)-D was correlated with 2.2 and 3.4 % decrease in the presence and severity of NCV impairment, respectively. While adjusted for demographic variables, comorbidities and treatment of DM, our results imply that decreased levels of circulating 25(OH)-D may contribute to increased risk of large fiber neuropathy in type 2 diabetic subjects.