Metformin is associated with worse cognitive function in older adults, which could be explained by B-vitamin deficiency, research suggests.

An association between long-term metformin treatment and vitamin B12 malabsorption was first reported more than 40 years ago, writes Dr Kirsty Porter, of Ulster University in Coleraine, Northern Ireland, and colleagues.

Deficiencies in B12, along with folate, vitamin B6 and riboflavin, have also been linked to cognitive dysfunction, they add in their study published in the Journal of Clinical Endocrinology and Metabolism.

To investigate the relationships among hyperglycemia, metformin use and B-vitamin status, they looked at 4160 community-dwelling, dementia-free older people participating in the Trinity, Ulster and Department of Agriculture study.