Prevalence of vitamin b12 deficiency in elderly with diabetes mellitus on metformin therapy and its association with cognition level

Abstract

Introduction: Vitamin B12 is indispensable for hematopoiesis and neurologic function. Metformin, the drug of choice for T2DM, has been noted to cause abnormal vitamin B12 absorption with prolonged therapy. Older patients are especially vulnerable because of age‐ related gastrointestinal changes and concomitant nutritional deficits. Aim: To assess the frequency of vitamin B12 deficiency among older patients with Type 2 diabetes who have been on metformin for a minimum of three years and assess its association with cognitive performance. Methods: In an 18-month, observational, cross-sectional study at our tertiary care hospital, 75 patients aged ≥60 years on metformin therapy (≥3 years) were enrolled. Patients with confounding conditions (e.g. pernicious anemia, gastrointestinal surgeries/disorders, chronic alcohol use, altered renal/hepatic function, or on proton pump inhibitors) were excluded. A structured questionnaire collected demographic data, metformin dose/duration, comorbidities, dietary patterns, and smoking status. A thorough clinical evaluation focused on neuropathic symptoms. Venous blood was drawn for serum vitamin B12 (categorized as deficient: <200 pg/mL, borderline: 200–400 pg/mL, or adequate: >400 pg/mL), blood sugar parameters, HbA1c, and other routine tests. Patients with vitamin B12 deficiency underwent cognitive evaluation using the Montreal Cognitive Assessment (MoCA). Statistical comparisons and multivariate logistic regression were performed using IBM SPSS version 30.0 with significance set at p < 0.05. Results: Overall, 21.3% (16/75) were vitamin B12 deficient. Only 2 patients on metformin for <5 years were deficient compared with 11 of 13 (84.6%) on therapy for >10 years. Deficient patients had a significantly lower mean MoCA scores (22 ± 3). Our result indicates that there is no statistically significant association between dietary habits (vegetarian vs. non-vegetarian) and Vitamin B12 levels in the cases with vitamin b12 deficient states. Conclusion: Elderly with type 2 diabetes mellitus who have been on long-term metformin treatment face a considerable risk of vitamin B12 deficiency, a condition that is closely linked to peripheral neuropathy and could also play a role in cognitive decline. Routine screening and early intervention in this high-risk population are recommended.