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Brittany Hambleton
Brittany Hambleton
January 4, 2024 ·  4 min read

Metformin Treatment Linked to Slowed Cognitive Decline

This article was originally published on October 1st, 2020, and has since been updated.

When someone has uncontrolled diabetes, there is too much sugar circulating in their blood. Over time, this can damage a person’s organs- including the brain. It is becoming more and more apparent that individuals with Type 2 diabetes are at a higher risk of developing Alzheimer’s [1]. New research, however, has found a possible solution. Scientists are finding that the diabetes drug metformin may help prevent cognitive decline.

Diabetes and Cognitive Decline

Both type 1 and type 2 diabetes predisposes people to cognitive decline, leading to dementia. Type 2, however, appears to create a greater risk. People with type 2 diabetes have a fifty percent greater risk of developing dementia. 

They are also more likely to experience impaired attention, processing and motor speed, executive functioning (thinking and self-control), and verbal memory [2].

As the number of people with diabetes continues to rise, and the lifespan of those people continues to lengthen, the prevalence of diabetes-related cognitive impairment places a significant strain on the healthcare system.

The link between cognitive decline and diabetes is extremely important. Doctors don’t yet fully understand how the two are connected, but they do know that having high blood sugar or insulin can affect the brain in the following ways:

  • Diabetes raises the risk of heart disease and stroke, which hurt the heart and blood vessels. Damaged blood vessels in the brain may contribute to cognitive decline.  
  • The brain depends on many different chemicals, which may be unbalanced by too much insulin. Some of these changes may help trigger cognitive decline.  
  • High blood sugar causes inflammation. This may damage brain cells and cause dementia to develop [1].

Research has shown a strong correlation between Alzheimer’s and high blood sugar. People with type 2 diabetes also have a much higher level of beta-amyloid protein, which is toxic to brain cells.

Even people in the early stages of type 2 diabetes have shown signs of brain dysfunction. Researchers have found that even people who had diabetes for less than ten years had deficits in memory function [1].

Metformin Slows Cognitive Decline

Researchers in Australia recently conducted a study of over one thousand Australians between the ages of seventy and ninety. They found that patients with diabetes who used metformin experienced slower cognitive decline. They also had lower rates of dementia compared to those who did not use the drug [3].

Researcher performed the study at the Garvan Institute of Medical Research and the Centre for Healthy Brain Ageing (CHeBA), UNSW Sydney, and published in the Journal Diabetes Care

Professor Katherine Samaras is the leader of the Healthy Ageing Research Theme at the Garvan Institute and endocrinologist at St Vincent’s Hospital Sydney. She says that their research promises new potential for a medication that is already widely used that we know is safe. This could be life-changing for patients and their families.

“For those with type 2 diabetes, metformin may add something extra to standard glucose lowering in diabetes care: a benefit for cognitive health,” she said [3].

In this study, 123 participants had type 2 diabetes. 67 of them used metformin, and the rest did not. The researchers tested their cognitive function every 2 years, including tests for memory, executive function, attention and speed, and language.

Participants taking metformin had a significantly slower cognitive decline and lower risk of dementia than those who were not taking the drug. In fact, participants taking metformin experienced the same rate of cognitive decline over six years as those who did not have diabetes at all [3].

A New Use for an Old Drug

One of the most significant benefits of these findings is that metformin has already been used to safely treat diabetes for sixty years. This means that medical researchers don’t have to develop a new drug to address the problem, a process that takes much more time and money.

Other studies have proven that metformin can be beneficial for other health issues, including cancer, heart disease, polycystic ovary syndrome and weight management. Samaras says that this new research means metformin may be useful to prevent cognitive decline more broadly.

“While type 2 diabetes is thought to increase dementia risk by promoting degenerative pathways in the brain and nerves, these pathways also occur in others at risk of dementia and it is possible insulin resistance may be the mediator,” says Professor Samaras [3].

In other words, metformin may be useful for people without diabetes, but who are experiencing cognitive decline. The researchers are now planning a much larger study to assess the efficacy of metformin in individuals at risk of dementia.

Professor Perminder Sachdev, senior author of the study and Co-Director of CHeBA, says that this study, which is observational in nature, does not provide definitive proof that metformin protects against dementia. It does, however, encourage researchers to do further study.

“The intriguing question is whether metformin is helpful in people in those with normal glucose metabolism. More work is clearly needed,” he said [3].

Samaras is hopeful that further study will answer that question.

“This may translate to us being able to repurpose this cheap medication with a robust safety profile to assist in preventing against cognitive decline in older people,” explained Samaras [3].


  1. Diabetes and cognitive decline.” ALZ
  2. Diabetes and Cognitive Impairment.” NCBI. Lindsay A. Zilliox, et al. July 2017.
  3. Metformin treatment linked to slowed cognitive decline.” Medical Xpress. Garvan Institute of Medical Research. September 23, 2020.