Wingo asked
Does metformin cause memory loss? I feel as though the longer I have been on the drug, I have gotten worse.
Answer
For years, there has been conflicting evidence on whether or not metformin, the most widely used diabetes medication worldwide, causes memory loss or impairment. Current evidence suggests that metformin does in fact have a negative effect on memory, although more studies are needed.
Interestingly, early studies indicated that metformin showed potential promise in treating and preventing certain neurological conditions such as Alzheimer's Disease and Parkinson's Disease. In Vitro studies (i.e. studies conducted in the lab in a non-biological context) showed that metformin could prevent the formation of amyloid beta peptides, one of the hallmarks of neurodegeneration in Parkinson's Disease.
Furthermore, studies in mice have shown that metformin promoted neurogenesis (i.e. generation of new neurons) and enhanced memory in rodents, as well as a overall reduction in oxidative stress.
Unfortunately, these past results don't seem to have transferred over to the human use of metformin. Many current studies now show that metformin is associated with cognitive decline. In fact, there have been studies that suggest a nearly two fold increase in the likelihood of mental impairment in those taking metformin versus those who are not. Worse yet, metformin has been linked to an increased risk of developing dementia and Parkinson's Disease.
One study followed over 9,000 patients for up to 12 years and found that the risk Parkinson’s disease, as well as dementia, increased over 50 percent during that period in those who took metformin. They concluded that long term metformin exposure in patients with diabetes may lead to the development of neurodegenerative diseases.
The problem with most of the studies linking metformin to cognition problems is that they are studies that simply accumulate data and do not control for conflicting factors such as other medications they may be taking, pre-existing conditions, familiy history of neurodegenerative disease etc... so it is impossible to conclusively say whether or not metformin definitively causes these problems. More large scale, well designed studies are needed to determine cause and effect.
Having said all that, metformin is known to cause a deficiency of Vitamin B12, which could be the leading factor in potential cognitive impairment. Current data indicates that up to 1 in 14 patients taking metformin for a period of 4 years develops Vitamin B12 deficiency and it is more likely common with high doses and longer use. A deficiency of Vitamin B12 is known to cause a slew of issues including nerve pain and anemia.
For this reason, it is often recommended to have your Vitamin B12 levels checked at least once yearly and supplement with Vitamin B12 if needed. Studies like this one have shown that supplementing with both calcium and Vitamin B12 can help reduce the symptoms of cognitive impairment from metformin. Ask your doctor about ways to supplement with Vitamin B12. Most may recommend up to 2000 mcg/day by mouth. It is available in injectable form as well for those with more moderate to severe deficiency.
