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

Key Takeaways

• Type 3 diabetes is a term used to describe insulin resistance in the brain, which researchers believe may contribute to Alzheimer’s disease. 
• Insulin plays a crucial role in brain health, and impaired insulin signaling can disrupt memory, learning, and cognitive function. 
• Lifestyle changes, blood sugar management, and cognitive training may help lower your risk of developing Alzheimer’s linked to insulin resistance. 

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You’ve probably heard of diabetes, but what about type 3 diabetes? Though it isn’t an official diagnosis, the term is becoming more common to address metabolic changes in our brains and nervous systems when we have prolonged high blood sugar levels.¹ 

Essentially, when the brain becomes insulin resistant, there may be an increased risk for cognitive decline and dementia symptoms as we age. 

As both diabetes and Alzheimer’s rates continue to rise, understanding this connection can help protect long-term brain health. Let’s take a look at the science behind this phenomenon, what we currently know from the research, and how you might be able to reduce your risk. 

Understanding Type 3 Diabetes 

Type 3 diabetes refers to the chain reaction of events that take place over a lifetime: high blood sugar that leads to insulin resistance, which ultimately triggers cognitive decline. Unlike type 1 diabetes, which is autoimmune, type 3 diabetes specifically affects the central nervous system and brain health.¹ 

However, type 3 diabetes isn’t necessarily a separate disease. When you have prolonged elevated or uncontrolled blood sugar levels, your body produces more insulin to help control it. As you produce more insulin, your body can become less responsive to insulin being available all the time. Think of it as a solicitor who keeps knocking on your door — eventually, you’ll stop answering. That’s what happens with insulin resistance. The cells stop answering the door to let blood sugar in when insulin comes knocking.¹

Over time, this means blood sugar levels rise. High blood sugar is associated with negative health outcomes and diabetes complications. Type 3 diabetes and its associated symptoms — worsening cognition and dementia — are two major associations with high blood sugar levels and insulin resistance.¹

Remember, this takes years or decades to impact your health. If you’re living with diabetes, there is a lot that you can control now to improve your health. 

The Role of Insulin in the Brain 

Insulin is a hormone produced by the pancreas that helps us regulate blood sugar, but it also plays a role in brain function.² 

Within the brain, insulin also supports: 

• Neuron growth: Insulin helps brain cells (neurons) grow, stay healthy, and live longer, like giving your brain cells the nutrients they need to thrive.
• Synaptic plasticity: Synaptic plasticity is a fancy way of describing how your brain adapts, learns, and remembers things over time. Synapses impact your brain’s ability to learn and adapt by forming new connections between brain cells. Insulin helps make those connections stronger. 
• Learning and memory: Insulin affects how your brain takes in new information and stores it as memory. It helps your brain “save files” for later so you can remember what you’ve learned. 

You can see how if brain cells are insulin-resistant, they may struggle to grow and survive, and they can’t get the fuel they need to function, adapt, or store memories. Over time, this can lead to cognitive changes or cognitive impairment, memory issues, and other symptoms associated with Alzheimer’s and dementia. 

Mechanisms Linking Insulin Resistance to Alzheimer’s Disease 

How exactly might insulin resistance create the perfect storm for Alzheimer’s disease? Scientists have identified a few possible mechanisms.³ 

Amyloid Beta Accumulation 

Amyloid beta accumulation is a buildup of sticky protein pieces in the brain. Normally, your brain is good at clearing these out, but when there’s insulin resistance, that cleaning process also doesn’t work. As a result, these sticky amyloid beta proteins start piling up and forming clumps.

These clumps of protein, also called amyloid plaques, can settle between brain cells and block blood flow and the messages they’re trying to send to each other. This is how neurons and synapses are affected; over time, this buildup disrupts memory, thinking, and communication. 

Tau Proteins 

Tau proteins act like tiny railroad tracks inside your brain cells, helping move nutrients and other important materials around. These tracks stay straight and organized when everything works normally, helping your brain function smoothly. 

But this system can go off track when insulin signaling is disrupted, like with long-term insulin resistance. The tau proteins start to change shape and get tangled. Without an organized system, our brains can’t function the same way. This is one mechanism that may explain memory loss and cognitive decline. 

Neuroinflammation 

Neuroinflammation means inflammation in the brain, like your brain’s immune system being stuck in “high alert” mode for too long. 

Normally, inflammation helps protect the body when you’re sick or injured, but it can do more harm than good when it becomes chronic. Chronic inflammation can damage healthy brain cells and disrupt how they work together in the brain. 

Phenomena like insulin resistance can fuel this constant state of inflammation. Over time, this can wear down brain tissue, making it harder to think clearly and increasing the risk of memory problems and cognitive decline, including conditions like Alzheimer’s. 

Risk Factors for Developing Type 3 Diabetes 

While not everyone with diabetes develops Alzheimer’s, certain factors may increase your risk for both conditions, especially where insulin resistance is involved:⁴ 

• Type 2 Diabetes: Research shows that people with type 2 diabetes have a significantly higher risk of Alzheimer’s, likely due to shared pathways involving inflammation, insulin resistance, and vascular damage. 
• Obesity: Carrying excess weight, especially around the abdomen, is associated with higher insulin levels and greater inflammation, risk factors for cognitive dysfunction. 
• Genetic Predisposition: Family history and the presence of certain genes, such as APOE4, may increase your risk of dementia, especially when combined with insulin resistance or type 2 diabetes.

Symptoms and Diagnosis 

The symptoms of type 3 diabetes mirror those of Alzheimer’s disease, since the underlying idea is that brain-based insulin resistance contributes to dementia. 

Common symptoms include: 

• Memory loss 
• Difficulty concentrating or processing information 
• Behavioral changes 
• Confusion or disorientation 

Diagnosing type 3 diabetes is challenging because there’s no specific test for insulin resistance in the brain. Alzheimer’s disease is typically diagnosed through clinical evaluations, cognitive testing, brain imaging, and sometimes spinal fluid analysis. 

Researchers are developing better tools to detect early metabolic changes in the brain that we might see years or decades before someone experiences cognitive changes. 

Prevention and Treatment Strategies 

Although there’s no known cure for Alzheimer’s disease, addressing insulin resistance may offer a promising path for prevention and management. 

Lifestyle Modifications 

Simple changes to your daily habits can go a long way in protecting your brain and supporting insulin sensitivity. Things like moving your body regularly, eating a Mediterranean-style diet (think veggies, whole grains, healthy fats like olive oil, and lean proteins), getting good-quality sleep, and reaching a healthy weight can all reduce inflammation and improve how your body—and brain—respond to insulin. 

Of course, diet and exercise impact blood glucose, cholesterol, lipid levels, and high blood pressure. Also known as metabolic syndrome, improving these markers through your lifestyle may slow or prevent disease progression, affecting everything from diabetes complications to the development of Alzheimer’s. 

Start with a 20-minute walk after dinner and swap sugary snacks for fruit or nuts. Aim for 7–8 hours of sleep each night to give your brain time to recharge. 

Pharmacological Interventions 

Researchers are exploring whether certain diabetes medications could also help protect the brain. For example, metformin, a common drug for type 2 diabetes, and intranasal insulin, which delivers insulin directly to the brain, are being studied for their potential to slow memory loss and cognitive decline in people with insulin resistance or early Alzheimer’s.⁵

If you live with diabetes or insulin resistance, talk to your healthcare provider about your treatment options and whether any of these pharmacotherapies might be right for you. 

Cognitive Training 

Just like your muscles, your brain benefits from regular exercise. Puzzles, reading, learning a new language or hobby, and even certain apps can help keep your mind sharp. These kinds of mental challenges help build what experts call “cognitive reserve,” which is like a buffer that may help delay symptoms of memory loss or dementia.⁶ 

Challenge yourself to do one new brain-boosting activity each week, like a crossword puzzle, memory game, or even if you’re feeling up to a challenge, learning a few words in another language. 

The Bottom Line 

The connection between Alzheimer’s disease and impaired insulin signaling in the brain is gaining attention. The good news is that managing your blood sugar, maintaining a healthy weight, and prioritizing physical and mental health may not only reduce your diabetes risk but also help protect your brain for years to come. 

Read Next: 7 Day Diabetes Meal Plan 

Learn More About How to Improve Blood Sugar Health With Signos’ Expert Advice 

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Learn more about how Signos can improve your health, explore helpful tips on glucose levels on the Signos blog, or take a quick quiz to see if Signos is a good fit for your goals.