Is Alzheimer's Actually A Type Of Diabetes? Some Researchers Think So

Though it doesn’t currently have a cure – or even a single diagnostic test – some researchers are beginning to see dementia as potentially “treatable”. 

A recent report from Alzheimer’s Disease International (ADI) and health writer Paul Gallagher showed that experts have become “optimistic” about the disease due to newly released drugs and an “unprecedented” boom in dementia research.

An older addition to that corpus is a 2020 paper that suggests that dementia could be considered a third kind of diabetes. 

It says that the relationship between poorly-controlled blood sugar and dementia onset is “so strong that some have called Alzheimer’s ‘diabetes of the brain’ or ‘type 3 diabetes (T3D)’”.

How is diabetes linked to dementia?

Alzheimer’s Society shared that people with type 2 diabetes (when the body becomes more resistant to the sugar-regulating hormone, insulin) are more likely to develop dementia than the general population. 

The same is also true of those with type 1 diabetes, which is an autoimmune condition where the body attacks its own insulin-making cells.

And the longer you live with either form of the condition, the greater your risk may be. 

This, Alzheimer’s Society explained, might be partly down to diabetes’ links with other risk factors – like high blood pressure and high cholesterol. 

But, they added, “some of the changes that occur in Alzheimer’s disease are similar to those in diabetes”. 

Like the 2020 review, they said: “Alzheimer’s disease is sometimes unofficially known as type 3 diabetes.”

In what ways are dementia and diabetes similar? 

Some studies suggest it could be down to insulin.

In both type 1 and type 2 diabetes, the body can become more resistant to insulin (which turns food into energy and manages your blood sugar).

Though a 2014 paper suggested the brain was considered an “insulin-insensitive organ”, experts now think it might produce the hormone. In fact, this article for The Conversation argues that the still-”unknown” source was discovered among rats in the ’70s, and then forgotten.

And brain insulin resistance may be a “common and early feature of Alzheimer’s disease”, a 2015 paper points out. A later 2017 study found that the markers of brain insulin resistance appeared to be linked to “tau and beta-amyloid pathologies”.

Amyloid plaques are sticky bundles of abnormal protein fragments, while tau tangles are made up of stringy proteins. Combined, this pair has been compared to the “trigger and bullet” in the development of dementia.

The APOE4 gene, a known dementia risk factor, has been linked to problems with how the brain uses and processes insulin in some research. Perhaps this dysregulation “starves” some brain cells, which rely on glucose (basically, sugar) to survive, said researchers.

Insulin sprays have also given mixed, but sometimes promising, results among those with mild cognitive impairment (often seen as a precursor to dementia) and Alzheimer’s disease.

A 2025 systematic review of so-called “type 3 diabetes” said that Alzheimer’s disease is “increasingly associated with metabolic dysfunction, particularly insulin resistance, which impairs neuronal signaling and energy metabolism”.

Ultimately, this area needs more research, and we know lots of factors could go into the development of dementia. 

But, the 2025 paper reads, this could “represent a critical area of research, linking metabolic dysfunction with neurodegeneration”.