Association of Vitamin D Level and Nerve Conduction Study Parameters with Cognitive Function in Diabetic Neuropathy Patients

Abstract

BACKGROUND: Type 2 diabetes mellitus (T2DM) and its major long-term complication, diabetic polyneuropathy (DPN), continue to be a major global health problem and are important contributors of significant disability worldwide. Vitamin D plays a significant role in their pathogenesis as well as in the development of dementia in non-diabetic patients. Nevertheless, the role of Vitamin D in the development of cognitive impairment in DPN patients has not yet been extensively studied. AIM: We aimed to investigate the association between Vitamin D level and cognitive function in DPN patients and to evaluate several potential contributor factors to cognition, including demographic factors, glycemic control, and nerve conduction study (NCS) parameters. METHODS: Thirty-one DPN patients were included in this cross-sectional study. Patients were recruited from the outpatient endocrinology and neurology clinic of Haji Adam Malik General Hospital Medan Indonesia. We used the diabetic neuropathy examination (DNE) scale, diabetic neuropathy symptom (DNS) scale, and NCS to determine the presence and severity of the neuropathy. We measured the levels of Vitamin D, random blood sugar, and glycated hemoglobin (HbA1c). Cognitive function was assessed using the Indonesian version of Montreal Cognitive Assessment (MoCA-INA), trail making test A and B (TMT A and TMT B), and verbal fluency test. RESULTS: Most of the patients were female (80.6%), with a mean age of 55.71 ± 8.34 years. The proportion of patients with abnormal cognitive function was higher than cognitively unimpaired patients. The mean of MoCA-INA score and level of Vitamin D was lower than normal, 23.32 ± 3.00 and 24.91 ± 13.59 ng/ml, respectively. Using the Pearson correlation test, we did not find any significant association of Vitamin D level, NCS parameters, and other clinical characteristics with global cognitive function. Age and level of education were significantly associated with MoCA-INA score. Blood sugar level was significantly higher in patients with normal TMT-A and TMT-B tests compared to patients with abnormal results. CONCLUSION: Vitamin D and NCS parameters are not associated with cognitive function. Of the demographic and clinical characteristics, a significant association exists between age, level of education, and blood sugar level and cognition. This might suggest the complexity underlying cognitive impairment in T2DM patients.