In a retrospective study, diabetic patients who were taking metformin had worse cognitive performance than those not taking the drug (odds ratio 2.23, 95% CI 1.05-4.75), Eileen Moore, PhD, of the University of Melbourne in Australia, and colleagues reported online in Diabetes Care.

Additionally, patients with diabetes who had vitamin B12 levels less than 250 pmol/L also had worse cognitive performance (OR 2.29, 95% CI 1.12-4.66), and the association between metformin and cognitive impairment was weakened after adjusting for vitamin B12 levels, they stated.

via In Some Patients Metformin Impairs Thinking.