Vitamin B12, Homocysteine and Cognitive Impairment in Elderly Patients with Type 2 Diabetes

Background: Type 2 diabetes (T2DM) increases the risk of mild cognitive impairment (MCI); however, the mechanisms of this process have not yet been fully identified. The aim of the study was to determine the levels of vitamin B12 and homocysteine in elderly diabetic patients, with and without cognitive impairment, and identify the risk factors associated with MCI in this group. Methods: A total of 385 elderly diabetic patients were screened for MCI (using the Montreal Cognitive Assessment). Several clinical and biochemical data were recorded. Results: MCI subjects had lower vitamin B12 levels (251 ± 36.9 pg/mL) and higher homocysteine concentrations (15.9 ± 4 ng/mL) compared to controls (vitamin B12: 339.9 ± 40.7 pg/mL; homocysteine: 11.4 ± 3.1 ng/mL). In MCI subjects, vitamin B12 levels were negatively correlated with homocysteine or HbA_1c levels and positively correlated with MoCA scores. The univariate logistic regression showed factors associated with MCI in elderly diabetic patients were the following: older age and fewer years of education, longer history of diabetes, a higher number of co-morbidities, higher levels of HbA_1c, triglycerides and homocysteine, lower levels of vitamin B12, presence of cardiovascular disease, hypertension, hyperlipidemia, retinopathy, and nephropathy. Independent factors associated with MCI evaluated in the multivariate model included lower levels of vitamin B12, higher levels of triglycerides, and a higher number of co-morbidities and fewer years of formal education. Conclusions: Vitamin B12 is associated with MCI in elderly diabetic patients. The role of homocysteine and vitamin B12 in the common pathogenesis of cognitive impairment and diabetes requires future prospective and more extensive studies.