A Cross-sectional Study on Prevalence of Vitamin B12 Deficiency and Peripheral Neuropathy between Metformin Users and Non Users in Participants with Type 2 Diabetes Mellitus

Abstract

Introduction: Metformin is a first line drug for treatment of Type 2 Diabetes Mellitus (T2DM) which acts by decreasing insulin resistance. Metformin use can lead to vitamin B12 deficiency. Aim: To evaluate the difference in proportion of vitamin B12 deficiency and clinical neuropathy between metformin users and metformin non users in patients with T2DM. Materials and Methods: This cross-sectional study was conducted at Department of General Medicine, Vydehi Institute of Medical Sciences and Research Centre, Bengaluru, Karnataka, India, from Jul 2015 to June 2017. Hundred patients with T2DM were recruited in the study, and divided into two groups i.e., T2DM patients on metformin (n=50) and without metformin (n=50). One group were patients of diabetes who were on metformin for more than three years, and the other group were those who had not taken metformin in last three months. All participants were evaluated with serum vitamin B12. Toronto Clinical Neuropathy (TCN) score was used to diagnose peripheral neuropathy. Multivariable logistic regression was done to look for association between metformin use and vitamin B12 deficiency and peripheral neuropathy separately. Results: Between the metformin users and non metformin user group, the proportion of males (72% vs 66%, p-value=0.66) and the age (56.02±9.19 vs 56.16±8.33 years, p-value=0.93) were similar in both groups. Median duration of diabetes among metformin users was 10.18 years (IQR=6.68-16.68 year) and non metformin user group was 7.68 years (IQR=5.68-12.68 year). There was a significantly higher prevalence of vitamin B12 deficiency in metformin users (38,76%) than non metformin users (21,42%). The prevalence of vitamin B12 deficiency was highest (11,100%) in those with metformin use for more than 15 years. Association of vitamin B12 deficiency in metformin users was significant {(OR=7.17 (2.46-20.92), p-value<0.001}. Peripheral neuropathy assessed by TCN scoring was significantly more common in metformin users (37,74% vs 23,46%; p-value=0.004). Conclusion: This study reports high prevalence of vitamin B12 deficiency in T2DM patients with significantly higher prevalence among metformin users. Peripheral neuropathy was significantly more common in metformin users and was associated with vitamin B12 deficiency. Hence, metformin treated T2DM patients, especially those with peripheral neuropathy should be evaluated for vitamin B12 deficiency.

Keywords

• glycated haemoglobin
• hypovitaminosis
• toronto clinical neuropathy scale