Alzheimer's and Diabetes: What's the Link?

Medically Reviewed by Christopher Melinosky, MD on September 11, 2022

Research shows that people with prediabetes or type 2 diabetes have a higher risk of getting Alzheimer's disease and other types of dementia later in life.

Scientists think there are a few ways that problems with blood sugar control can lead to problems with your memory and thinking.

Insulin Resistance

When your cells don't use insulin the way they should, that affects the mechanics of your brain.

  • Your cells don't get the fuel they need, so your brain can't work right.
  • Your blood sugar goes up, and over time, that can cause harmful fatty deposits in your blood vessels.
  • Too much insulin can throw off the balance of chemicals in your brain.

These effects on the brain are so strong that some scientists feel that Alzheimer's related to insulin resistance should be called "type 3 diabetes."

Inflammation and Blood Vessel Damage

With diabetes, you're at greater risk for a heart attack or stroke. And high blood sugar levels can trigger inflammation. None of that is good for your blood vessels. Damaged vessels in your brain could lead to Alzheimer's.

Inflammation can also make your cells insulin resistant, especially if you're obese.

Blocked Nerve Communication

High blood sugar has been linked to higher levels of protein pieces called beta amyloid. When these clump together, they get stuck between the nerve cells in your brain and block signals. Nerve cells that can't talk to each other is a main trait of Alzheimer's.

Tangled Tau Protein

Your cells are constantly moving food and other supplies along pathways like railroad tracks. A protein called tau helps these tracks that run into, out of, and through the cells stay in straight rows.

But in a brain with Alzheimer's, tau gets tangled up. The tracks fall apart, and cells die because they can't move stuff to where they need it.

Some studies suggest that people with diabetes have more tangled tau in their brains. That could mean they have more dying cells in their brains, which can lead to dementia.

What You Can Do

Manage your blood sugar levels. A few studies lead some scientists to believe that keeping your A1c below 7% may help your brain stay well.

Work out.Exercise will help your cells use insulin better and help you manage your blood sugar and avoid too much insulin in your blood and brain. Physical activity brings oxygen-rich blood to your brain, and it lowers your risk of heart disease.

Maybe metformin. In a study of more than 15,000 people older than 55 who had type 2 diabetes, those who took metformin (Fortamet, Glucophage, Glumetza, Riomet) were less likely to get Alzheimer's and other types of dementia than those who took other diabetes drugs.

Show Sources


American Diabetes Association: "Aerobic Exercise Improves Brain Function for People with Prediabetes," "Types of Activity: What We Recommend."

"Diabetes and Cognitive Decline," Alzheimer's Association, October 2015.

National Institute of Diabetes and Digestive and Kidney Diseases: "Diabetes, Heart Disease, and Stroke."

"Alzheimer's Disease and Type 2 Diabetes: A Growing Connection," Alzheimer's Association, 2007.

De la Monte, S.M. Journal of Diabetes Science and Technology, November 2008.

Harvard Health Publications: "What you eat can fuel or cool inflammation, a key driver of heart disease, diabetes, and other chronic conditions."

Chen, L. International Journal of Endocrinology, published online June 2, 2015.

Alzheimer's Association: "Brain Tour," "Brain Health: Stay Physically Active."

American Academy of Neurology: "Diabetes and Brain Tangles May Be Linked Independently of Alzheimer's Disease."

Kawamura, T. Journal of Diabetes Investigation, published online Aug. 29, 2012.

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