Exploring the Link Between Alzheimer’s and Insulin Resistance: Understanding Type 3 Diabetes.

by Rebecca Jaspan, MPH, RD, CEDS, CDCES

Are some cases of Alzheimer’s disease caused by a form of diabetes in the brain? Researchers are identifying another form of diabetes, known as type 3 diabetes. This type manifests as insulin resistance in the brain and has potential to impact neurocognition, contributing to Alzheimer’s disease. While not universally adopted, many in the medical community are beginning to label Alzheimer’s disease as type 3 diabetes. Physicians, researchers, and nutritionists for diabetes are noticing similarities between how diabetes and Alzheimer’s affects the brain and cognition and some are even classifying Alzheimer’s disease as type 3 diabetes.

What is Alzheimer’s Disease?

Alzheimer’s disease affects over 5 million people in the United States. It is a type of dementia that affects memory, thinking, and behavior. Alzheimer’s is a progressive disease and over time, symptoms grow severe enough to interfere with daily tasks. A risk factor for Alzheimer’s is increasing age and the majority of people with Alzheimer’s disease are 65 and older. Other risk factors include family history, genetics, head injury, excessive alcohol consumption, heart health, and poorly controlled blood sugars.1 Specifically prediabetes symptoms, insulin resistance and high blood sugars, have been linked to memory deficits, cognitive decline, and many other characteristic symptoms seen in Alzheimer’s disease.2

How Insulin Plays a Role

In order to understand the relationship between diabetes and Alzheimer’s disease, it is important to examine the role of insulin in the brain. Insulin performs many essential functions in the brain related to the regulation of food intake, body weight, eating habits, and homeostasis of energy. It also appears to act as a regulator of long-term memory enhancement and suppression.3 Further, Alzheimer’s disease and type 2 diabetes are both diseases that contribute to the formation of amyloid plaques, which are abnormally configured proteins that play a critical role in the formation of Alzheimer’s disease. The accumulation of these amyloids is involved in the progression of Alzheimer’s disease. Research shows that insulin dysfunction, one of the causes of inflammation, enhances the concentration of these amyloids.4

How Is Type 3 Diabetes Diagnosed?

While there is no specific test to diagnose type 3 diabetes, clinicians will look for both signs of Alzheimer’s disease and type 2 diabetes. To diagnose Alzheimer’s, a physician will take a full medical history, ask about family history, perform a neurological exam, administer neurophysiological testing, and recommend imaging studies of the brain. Type 2 diabetes patients are not routinely evaluated on their cognitive status and Alzheimer’s disease patients are not routinely evaluated for high levels of insulin and poor blood sugar control. Studies are suggesting that Alzheimer’s disease is a metabolic disease caused by insulin resistance in the brain and offers strong support for evaluation in both types of health conditions.5 Working with a diabetes dietitian, or a Certified Diabetes Care and Education Specialist (CDCES), can help you make changes to your diet and lifestyle to contribute to the prevention of both type 2 diabetes and Alzheimer’s disease.

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