More than one in four adults over the age of 65 develops diabetes. This condition damages the pancreas, making it hard for the body to control blood sugar. Because blood sugar plays a key role in powering the brain, diabetes and brain health issues, including Alzheimer’s and other forms of dementia, have some serious overlap.

They are so closely linked, in fact, some researchers have even dubbed Alzheimer’s “Type 3 diabetes.”

What is diabetes?

Diabetes is the umbrella term for a group of similar chronic diseases that result in too much sugar — also called glucose — in the blood.

Type 2 diabetes is a condition that affects the way the body processes glucose in the blood. In Type 1 diabetes, the pancreas produces little or no insulin.

In short, if you have diabetes, your body is having trouble turning food into energy. Your body breaks down most of the food you eat into glucose which makes its way into your blood, traveling around your body and delivering energy — including to your brain. The pancreas plays a role in this fuel system, too. It produces a hormone called insulin, which helps make sure the levels of glucose in your bloodstream don’t get too high.

Why does diabetes affect brain health?

Sugar is the main source of fuel for the brain.  If there’s a problem with the delivery system, and the brain isn’t getting the right amount of glucose — possibly due to an issue with the ability of the pancreas to produce insulin — the brain starts to slow down as it runs out of fuel, and that leads to fatigue, brain fog, and problems with memory. 

These cognitive issues can be short-term, but scientists are looking into the long-term effects of this breakdown on the brain, too.  Diabetes has been found to lead to permanent cellular damage in the brain, and this, researchers say, might be the reason why it, in turn increases a person’s chances of developing dementia in their lifetime or experiences dementia earlier than they would have otherwise by as much as double.

Diabetes and the “Alzheimer’s gene”

The APOE gene is the human body’s instruction manual for building apolipoprotein, a protein that grabs and carries cholesterol throughout the body. Everyone carries two copies of this gene — and it comes in a few variants. One of these variants, APOE4, has been found to increase a person’s chances of developing cardiovascular disease — and Alzheimer’s disease. 

People carrying one or two copies of this gene are worse at clearing disease-causing beta-amyloid plaques in the brain, making them more susceptible to Alzheimer’s.

Interestingly, APOE4 is a risk factor for diabetes, too. People who carry this genetic variant are more likely to have issues with the pancreas’s ability to produce insulin and regulate blood sugar.

Race, diabetes and dementia

Researchers have also zeroed in on race as another factor that impacts disease risk — Black Americans are more likely to develop diabetes or dementia than white Americans.

Since the majority of medical research to date is conducted on white individuals, studies are seeking to diversify their participants to better understand this risk factor.

Prevention and treatment strategies for both diabetes and dementia

With so many shared risk factors between the two diseases, there is some good news. Many diabetes prevention strategies also reduce the risk of developing dementia.

A heart-healthy diet

A healthy Mediterranean or MIND-style diet reduces cholesterol and blood sugar. Some research suggests that these diets also lower the risk of dementia. These two similar diets consist of foods like:

      -Fruits, vegetables, and legumes 
      –Nuts and seeds
      -Whole grains
      -Seafood
      -Olive oil

Regular exercise

Physical exercise, which lowers blood sugar as the body mobilizes it to fuel the muscles, has also been shown to both reduce dementia risk and help prevent diabetes.  

Medications 

Medications that bring blood glucose under control, like metformin, have been found to lower Alzheimer’s risk in people who already have diabetes. 

Now, showing just how strong this link between brain health and blood sugar is, drug developers are testing drugs originally designed for diabetes as a potential treatment for Alzheimer’s. Diabetes and weight-loss drug semaglutide (brand names  Ozempic, Wegovy) is being tested as a way slow the progression of cognitive decline in Alzheimer’s. 

Combining lifestyle-based prevention strategies with new drugs that address these health conditions’ overlapping factors could bring us closer to helping people avoid both diabetes and dementia.