What Is Type 3 Diabetes?

Someone pricking their finger to test blood sugar levels
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Type 3 diabetes is a controversial name sometimes used to refer to Alzheimer's disease, a type of progressive dementia. Strong links have been made between the two conditions, most notably that dementia may be triggered by a type of insulin resistance occurring specifically in the brain.

According to the American Diabetes Association (ADA), aside from advanced age having diabetes or prediabetes is the second biggest risk factor for Alzheimer's disease. Although a small amount of research found an increased risk of dementia with type 1 diabetes, the vast majority of studies have concluded that this link between diabetes and Alzheimer's is specific to type 2 diabetes.

However, classifying Alzheimer's as type 3 diabetes is controversial, and many in the medical community are unwilling to recognize type 3 diabetes as a medical diagnosis until more research is done.

Note that type 3 diabetes is not the same as type 3c diabetes mellitus (also called T3cDM or pancreatogenic diabetes), a secondary condition that may arise as a result of other pancreatic diseases.

The Connection Between Alzheimer's and Diabetes

Studies show the risk of developing Alzheimer’s disease among people with diabetes is 65% higher than that of those without diabetes. With such a strong link, research has focused on explaining the connection between the two diseases.

In type 1 diabetes, which is an autoimmune disease, the cells that produce insulin, called beta cells, are attacked by the body's immune system, causing glucose to build up to high levels in the bloodstream.

Type 2 diabetes occurs when insulin becomes less sensitive to glucose (sugar) and therefore less efficient at removing it from the bloodstream, allowing it to build up rather than being taken into the cells to be used for energy.

In Alzheimer's disease, it appears a similar problem of insulin resistance occurs, but rather than affecting the body as a whole, the effects are localized in the brain.

In studies of people's brains after death, researchers have noted the brains of those who had Alzheimer's disease but did not have type 1 or type 2 diabetes showed many of the same abnormalities as the brains of those with diabetes, including low levels of insulin in the brain. It was this finding that led to the theory that Alzheimer's is a brain-specific type of diabetes—"type 3 diabetes."

In diabetes, if a person's blood sugars become too high or too low, the body sends obvious signs of the problem: behavior changes, confusion, seizures, etc. In Alzheimer's disease, however, rather than those acute signals, the brain's function and structure decline gradually over time.

When a group of researchers reviewed the collections of studies available on Alzheimer's disease and brain function, they noted that a common finding in Alzheimer's disease was the deterioration of the brain's ability to use and metabolize glucose. They compared that decline with cognitive ability and noted that the decline in glucose processing coincided with, or even preceded, the cognitive declines of memory impairment, word-finding difficulty, behavior changes, and more.

Furthermore, scientists determined that as insulin functioning in the brain worsens, not only does cognitive ability decline, the size and structure of the brain also deteriorate—all of which normally occur as Alzheimer's disease progresses.

The term "type 3 diabetes" is used, therefore, in two circumstances: to describe an actual type of diabetes that only affects the brain and to describe the progression of type 2 diabetes to Alzheimer's disease.

Type 3 Diabetes Symptoms

The symptoms of type 3 diabetes are essentially the same as the symptoms of early dementia, which, according to the Alzheimer's Association, include:

  • Difficulty completing once-familiar tasks, such as driving to the grocery store
  • Memory loss that disrupts daily life
  • Challenges in planning or problem solving
  • Confusion with time or place
  • Trouble understanding visual images or spatial relationships, such as difficulty with reading or balance
  • Difficulty joining or following conversations or speaking/writing
  • Frequently misplacing things and being unable to retrace your steps
  • Mood or personality changes

Causes

For decades, researchers have attempted to determine the specific cause of Alzheimer's disease. Some research suggests that while diabetes likely exacerbates and contributes to the development of Alzheimer's disease, it is probably not the sole cause of it.

However, it is known that diabetes complications can affect brain health by:

  • Raising the risk of heart disease and stroke, which can lead to damaged blood vessels, which in turn can inhibit blood flow to the brain, resulting in dementia
  • Leading to an excess of insulin, which may alter the amount or status of other neurochemicals reaching the brain, an imbalance that may lead to Alzheimer's
  • Resulting in elevated blood sugar, which leads to inflammation that may damage brain cells and trigger Alzheimer's

Risk Factors

The primary risk factor for developing type 3 diabetes is having type 2 diabetes. The risk factors for developing type 2 diabetes include:

Diagnosis

Althought there's no dedicated test for type 3 diabetes, clinicians will typically look for signs of Alzheimer's and signs of diabetes.

To diagnose Alzheimer's, a doctor will:

  • Take a full medical history
  • Ask about your family history with regard to Alzheimer's and dementia
  • Perform a neurological examination
  • Administer neurophysiological testing
  • Recommend imaging studies, such as magnetic resonance imaging (MRI), which can give provide visual evidence of how the brain is functioning,and to look for the hallmark amyloid plaques—clusters of a protein called beta-amyloid—consistent with Alzheimer's

If you have symptoms of type 2 diabetes, your physician may also request that you do a fasting or random glucose test and a hemoglobin A1c (Hb A1c) test to see how well your blood sugar is being controlled.

Treatment

If you have been diagnosed with both type 2 diabetes and Alzheimer's, your physician may recommend a diabetes treatment protocol to help get your blood sugar levels under control.

Standard treatment for type 2 diabetes includes:

  • Lifestyle modifications such as weight loss, dietary changes, and exercise
  • Various drugs therapies including sulfonylureas, glucagon-like peptides, biguanides such as metformin, and others
  • Supplemental insulin, generally used only when lifestyle changes and other first-line drugs aren't effective
  • Frequent blood sugar monitoring and Hb A1c testing

There is potential that diabetes medications such as metformin and glucagon-like peptides may be helpful in preventing the progression of Alzheimer's. In animal and human studies, these medications have shown evidence of improving insulin sensitivity that may protect against the structural abnormalities that develop in Alzheimer's disease, improve the brain's ability to metabolize glucose, and demonstrate an improvement in cognitive functioning in some cases.

Pharmaceutical treatment for Alzheimer's has proven elusive. While there are several prescription medications designed to treat Alzheimer's symptoms, their effectiveness remains in question.

Many people with Alzheimer's have low levels of a neurotransmitter called acetylcholine.  Medications known as cholinesterase inhibitors, for example, Aricept (donepezil), Razadyne (galantamine), or Exelon (rivastigmine), may help by maintaining levels of acetylcholine in the brain.

Namenda (memantine), an NMDA-receptor antagonist, has been shown to marginally reduce the progression of the disease, and is usually prescribed alongside a cholinesterase inhibitor.

Behavioral symptoms such as depression, common in early Alzheimer's, are typically treated with selective serotonin reuptake inhibitors (SSRIs) such as Prozac (fluoxetine).

Alzheimer's medications are generally trialed first for eight weeks, then reviewed to determine if there's any benefit.

Prevention

There's a good deal of crossover between measures that can help to prevent both diabetes and Alzheimer's, such as following a healthy diet and increasing physical activity.

To reduce the risk of developing Alzheimer's disease specifically, follow these four pillars:

  1. Follow a diet rich in whole foods and low in processed, refined foods, and take a high-potency supplement. A good option is the Mediterranean diet.
  2. Get ample physical exercise—ideally 150 minutes of cardio and strength training each week—and mental exercise (by reading, creating art, doing crossword puzzles, and other cerebral activities.
  3. Deal with stress. Practices such as yoga and meditation can help.
  4. Enhance your psychological well-being by socializing with others and providing service in your community.

Numerous studies have revealed how lifestyle changes can improve glucose control in people with type 2 diabetes. In addition to the four pillars above, other measures that can help stave off diabetes include:

  • Losing 5% to 10% of your body weight to help restore insulin sensitivity
  • Quitting smoking to reduce the stress on your organs
  • Getting adequate sleep to reduce the effects of chronic stress and improve glucose absorption

A Word From Verywell

If you have diabetes and are concerned about your risk of developing Alzheimer's disease as a result, discuss your concerns with your physician. They may be able to fine tune your treatment and management strategies to help shore up your defense against Alzheimer's.

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