Scientists explore the emerging link between insulin resistance and Alzheimer’s disease

Research suggests that insulin resistance may play a key role in Alzheimer’s development, sparking renewed interest in the metabolic links between diabetes and neurodegeneration despite the term ‘Type 3 diabetes’ remaining unofficial.

Researchers are increasingly examining whether Alzheimer’s disease may be shaped by the same metabolic pathways involved in diabetes, even as doctors stress that “type 3 diabetes” remains an informal theory rather than an official diagnosis. HuffPost UK reported that a 2020 paper described the link between poor blood sugar control and dementia as strong enough that some scientists have called Alzheimer’s “diabetes of the brain”, while Alzheimer’s Disease International has recently pointed to a wave of new research and emerging treatments that has made experts more hopeful about the condition.

The idea rests largely on insulin. In diabetes, the body either does not make enough insulin or does not respond to it properly; several studies suggest similar problems may occur in the brain in Alzheimer’s disease. Healthline, Medical News Today and WebMD have each noted that some researchers use the phrase “type 3 diabetes” to describe the hypothesis that insulin resistance in the brain may contribute to memory loss and cognitive decline. ScienceAlert has likewise reported that the concept is gaining attention as scientists look more closely at the metabolic side of neurodegeneration.

That does not mean the term has been accepted by the wider medical community. Healthline said major diabetes organisations do not recognise “type 3 diabetes” as a formal condition, and the same caution appears in other explainers of the theory. Still, the underlying concern is not speculative: Alzheimer’s Society says people with type 1 and type 2 diabetes are at higher risk of dementia than the general population, and that the risk may rise with the length of time someone has lived with diabetes. The charity also notes that high blood pressure and high cholesterol may help explain part of that connection.

Some researchers believe the overlap may go deeper than shared risk factors. HuffPost UK reported that studies have linked brain insulin resistance with tau and beta-amyloid, two proteins closely associated with Alzheimer’s disease. Other work has suggested that genetic risk factors, including APOE4, may affect the way the brain handles insulin. Experimental insulin sprays have produced mixed results, but some early findings have been encouraging in people with mild cognitive impairment and Alzheimer’s.

For now, the science points to possibility rather than proof. The 2025 systematic review cited by HuffPost UK said Alzheimer’s disease is increasingly being associated with metabolic dysfunction, especially insulin resistance, and argued that this could become an important area for further research. Even so, experts continue to emphasise that dementia is a complex condition with many possible causes, and that any claim that it is simply a form of diabetes would be premature.