Diabetes mellitus (also called DM or diabetes for short) refers to a health condition where your body has difficulty converting sugar to energy. Typically, we think of two or three kinds of diabetes:

  • Type 1 diabetes (T1DM) is a chronic health condition in which your body’s endocrine part of the pancreas doesn’t produce enough of the hormone insulin, and your blood sugar (glucose) level becomes too high.
  • Type 2 diabetes (T2DM) is a chronic condition in which your body develops resistance to insulin, and your blood sugar level becomes too high as a result.
  • Gestational diabetes (GDM) is DM that occurs during a pregnancy, and the blood sugar level is too high during this time.

Some older and more recent research studies have proposed that Alzheimer’s disease should also be classified as a type of diabetes, called type 3 diabetes.

This “type 3 diabetes” is a term that has been proposed to describe the hypothesis that Alzheimer’s disease, which is a major cause of dementia, is triggered by insulin resistance and insulin-like growth factor dysfunction specifically in the brain, with dysfunction selectively in the brain similar to what happens in other parts of the body in types 1 and 2 diabetes.

This condition also has been used by some to describe people who have type 2 diabetes and are also diagnosed with Alzheimer’s disease dementia. The classification of type 3 diabetes is controversial, and most doctors aren’t ready to use it until more research is done.

The above “type 3 diabetes” medical condition isn’t to be confused with type 3c diabetes mellitus (also called T3cDM, pancreatogenic diabetes, and type 3c diabetes). The pancreas has both endocrine gland and exocrine glands and their respective functions. Insulin is one of the hormones that is produced and secreted by beta-islet cells in the Islets of Langerhans, which is endocrine pancreas tissue.

When the exocrine pancreas becomes diseased and then causes a secondary insult to the endocrine pancreas that ultimately leads to DM, this is T3cDM. Exocrine pancreatic diseases that may lead to T3cDM include pathology such as chronic pancreatitis, cystic fibrosis, and exocrine pancreatic cancer.

Keep reading to find out what we know, and what we don’t, about “type 3 diabetes,” and please keep in mind that this isn’t to be confused with type 3c diabetes.

There is already an established link between Alzheimer’s and type 2 diabetes. Since Alzheimer’s may be triggered by insulin resistance in your brain, some people say that Alzheimer’s is simply “diabetes in your brain.”

This claim has some science behind it, but it’s a bit of an oversimplification.

Over time, untreated diabetes can cause damage to your blood vessels, including the vessels in your brain. Since many people who have type 2 diabetes don’t know that they have the condition, which may delay diagnosis and appropriate treatment measures, those with type 2 diabetes have a higher risk of this kind of damage.

Diabetes also throws off the balance of chemicals in your brain, which may trigger Alzheimer’s. And high blood sugar leads to inflammation, which may damage brain cells.

For these reasons, diabetes is considered a risk factor for a condition called vascular dementia. Vascular dementia can be a stand-alone diagnosis with symptoms of its own, or it can be a warning sign of what will develop into overlap with Alzheimer’s disease.

The science of this is still shaky. For now, what’s been established is that there are cases of Alzheimer’s disease and other forms of dementia that don’t have any demonstrated link to insulin resistance.

People who have type 2 diabetes may be up to 60 percent more likely to develop Alzheimer’s disease or another type of dementia, such as vascular dementia. One study of over 100,000 subjects with dementia pointed out that women with type 2 diabetes had a higher probability of developing vascular dementia than men.

Risk factors for type 2 diabetes include:

The symptoms of type 3 diabetes are the same as symptoms of dementia, such as that seen in early Alzheimer’s disease. These symptoms include:

  • memory loss that affects daily living and social interactions
  • difficulty completing familiar tasks
  • misplacing things often
  • decreased ability to make judgements based on information
  • sudden changes in personality or demeanor

There’s no specific test for Alzheimer’s or type 3 diabetes. Your doctor will ask several questions about your family history and your symptoms. Imaging studies, like MRI and CT scans of the head, may give your doctor a picture of how your brain is working. Cerebrospinal fluid testing can also look for indicators of Alzheimer’s.

If you have the symptoms of type 2 diabetes and Alzheimer’s and haven’t been diagnosed with either one, you may be sent for a fasting blood sugar test and a glycated hemoglobin test.

If you do have type 2 diabetes, it’s essential that you begin treatment for it. Treating type 2 diabetes could minimize damage to your brain and slow the progression of Alzheimer’s or dementia.

There are specific treatment options for people who have pre-type 2 diabetes or type 2 diabetes, as well as Alzheimer’s. Lifestyle changes, such as diet and exercise, may be a big part of your treatment.

Losing 5 to 7 percent of your body mass can help stop organ damage caused by high blood sugar and may prevent the progression of pre-DM2 to DM2. A diet low in fat and rich in fruits and vegetables can also improve symptoms. If you smoke tobacco products, you’ll be advised to quit smoking.

If you have both type 2 diabetes and Alzheimer’s, treatment for your type 2 diabetes is important to help slow the progression of Alzheimer’s. Metformin is an anti-diabetes drug that may also reduce the risk of developing Alzheimer’s disease, compared to medications from other DM2 treatment classes.

Prescription medications are available to treat cognitive symptoms of Alzheimer’s dementia. Acetylcholinesterase inhibitors like donepezil (Aricept), galantamine (Razadyne), or rivastigmine (Exelon) can be prescribed to improve the way that your body’s cells communicate with one another. Memantine (Namenda), an NMDA-receptor antagonist, may also help to reduce symptoms and slow the progression of Alzheimer’s disease.

Other symptoms of Alzheimer’s and other dementia types, like mood swings and depression, may be treated with psychotropic drugs. Antidepressants and anti-anxiety medications are part of treatment in some cases. Some may need a light dose of antipsychotic therapy later in the course of the dementia process.

Type 3 diabetes is a way of describing Alzheimer’s that is caused by insulin resistance inside the brain. So your outlook will vary according to several factors, including your diabetes treatment.

If you can treat your diabetes with diet, exercise, and medication, you may be able to slow the progression of Alzheimer’s or vascular dementia.

Your outlook will also vary according to how soon your symptoms were discovered and what your doctor thinks about your specific case. The sooner treatment begins, likely the better your outlook will be.

The average life expectancy for a person with Alzheimer’s is around 3 to 11 years from the time that they’re diagnosed. But some people with Alzheimer’s can live as many as 20 years post-diagnosis.

If you already have type 2 diabetes, there are ways that you can help to better control it and lower your risk for developing type 3 diabetes. Here are some of the proven methods for controlling type 2 diabetes and minimizing organ damage:

  • Exercise four times per week for 30 minutes per day.
  • Eat healthy foods low in saturated fat, rich in protein, and high in fiber.
  • Carefully monitor your blood sugar according to your health team’s recommendations.
  • Take any prescribed medications on schedule and with regularity.
  • Monitor your cholesterol levels.
  • Maintain a healthy weight.