Type 3 diabetes is a title that has been proposed for Alzheimer’s disease which results from resistance to insulin in the brain.
Studies carried out by the research team at Warren Alpert Medical School at Brown University identified the possibility of a new form of diabetes after finding that insulin resistance can occur in the brain
Lead researcher, Dr Suzanne de la Monte, carried out a further study in 2012 to further investigate the link.
The researchers pinpoint resistance to insulin and insulin-like growth factor as being a key part of the progression of Alzheimer’s disease. 
Whereas type 1 and type 2 diabetes are characterised by hyperglycemia (increased blood sugar), a separate study, carried out by the University of Pennsylvania and published in 2012, excluded people with a history of diabetes, indicating that Alzheimer’s can develop without the presence of significant hyperglycemia in the brain.
type 3 diabetes is known as insulin resistance in the brain
INCREASED RISK OF ALZHEIMER’S
People that have insulin resistance, in particular those with type 2 diabetes have an increased risk of suffering from Alzheimer’s disease estimated to be between 50% and 65% higher.
Researchers have discovered that many type 2 diabetics have deposits of a protein called amyloid beta in their pancreas which is similar to the protein deposits found in the brain tissue of Alzheimer’s sufferers.