Insulin Resistance Raises the Risk for Alzheimer Disease

What do you know about your chance of developing dementia as you grow older? When it comes to the risk for Alzheimer disease, many people focus on genetic factors. People who have the e4 variant of the APOE gene are more likely to develop Alzheimer disease. However, genes are not the only influence. Over the past few decades, researchers have also been considering whether insulin resistance is a risk factor.

How Does Insulin Resistance Influence the Risk for Dementia?

According to one study, a readily available blood test for insulin resistance might reveal how quickly people with dementia will decline (Alzheimer’s & Dementia, Feb. 2025). Italian researchers tracked 315 non-diabetic patients who were experiencing cognitive decline. There were 200 people with confirmed Alzheimer disease in this group. The neurologists tested all volunteers for insulin resistance by employing the triglyceride-glucose index. This calculation, abbreviated TyG, is based upon readily available inexpensive blood tests. Patients who had high insulin resistance, as determined by the TyG index, declined much faster than people with lower insulin resistance.

The researchers point out that neurons need glucose to function properly. Insulin resistance seems to interfere with that process. Moreover, it is also associated with the accumulation of amyloid plaque within the brain. People with APOE e4 genetic susceptibility to Alzheimer disease are at greater risk.

How Can You Reduce Insulin Resistance?

People can reduce their insulin resistance by increasing physical activity and reducing their intake of highly processed carbohydrates, including sugary drinks. Losing excess weight can also make a difference.

How the Scientists Learned about the Risk for Alzheimer Disease:

Insulin resistance is often the first sign of type 2 diabetes. Researchers have known for a decade that increased insulin resistance puts the brain at risk for Alzheimer’s disease. In one early study from Wisconsin, investigators recruited people with an average age of 60 for an Alzheimer disease prevention study (JAMA Neurology, Sept. 2015). They used brain scans to see how well the brains were using fuel, and found that folks with insulin resistance were less efficient at burning energy in the parts of the brain first affected with Alzheimer disease.

This research did not follow people over time to see who developed Alzheimer disease or other dementia in the subsequent years. That study should be done in the future to verify these conclusions.

Even before Alzheimer disease could be diagnosed, people with insulin resistance had decreased cognitive function. Insulin resistance is linked to obesity, a sedentary lifestyle, a diet high in fructose and refined carbs as well as certain drugs, including statins.

Does Type 2 Diabetes Increase the Risk for Dementia?

A subsequent study compared adults with type 2 diabetes to those with healthy metabolism with respect to the risk for dementia (Journal of Clinical Medicine, July 26, 2024).  The researchers found that people who were not yet 50 years old when diagnosed with type 2 diabetes had an increased chance of developing dementia. Their risk was three times higher for any type of dementia, four times higher for Alzheimer disease and more than five times higher for vascular dementia.

What Can You Do to Change Your Chances of Developing Dementia?

Are you concerned about this connection between insulin resistance and the risk for Alzheimer disease? If so, you might want to follow a diet that lowers the likelihood of developing diabetes. You may also be interested in our interview with Dr. Dale Bredesen. In it, he describes a multifaceted plan for cutting the probability of an Alzheimer disease diagnosis or even reversing the disease if it has not progressed too far. We also interviewed him for Show 1132: Are Infections to Blame for Alzheimer Disease?  Dr. Bredesen also features in Show 1412: Beyond Amyloid: the Science That Could Change the Course of Alzheimer Disease.