Long-term use of the diabetes medication metformin may increase the risk for neurodegenerative disease in patients with type 2 diabetes mellitus (T2DM), new research suggests.

A study of over 7,000 patients with Alzheimer’s disease showed that, metformin increased the risk of developing Alzheimer’s . No large clinical trials have confirmed whether metformin is beneficial in non-diabetic Alzheimer’s patients.

In a cohort study that followed about 9300 patients with T2DM in Taiwan for up to 12 years, the risk for Parkinson’s disease (PD) or Alzheimer’s dementia was more than double during a 12-year period for those who took metformin vs those who did not — even after adjusting for multiple confounders. The use of metformin may be associated with an increased risk for dementia in older African Americans with diabetes. This research was presented at the 2018 Alzheimer’s Association International Conference, held July 22-26, 2018 in Chicago, Illinois.

Additionally, Metformin is associated with low vitamin B12 levels and people with profoundly low vitamin B12 levels can have significant cognitive impairment.