Cumulative exposure to impaired fasting glucose is not significantly associated with vascular dementia, while mild, chronic hyperglycemia contributes more to neurodegenerative processes such as Alzheimer’s disease than to cerebrovascular pathology.

Long-term high blood sugar causes brain cells to produce too much of a sticky protein called amyloid-beta and to twist another protein called tau in harmful ways. These changes build up inside brain cells, disrupt their function, and eventually kill them, leading to memory loss and thinking problems. This process happens without major damage to the brain's blood vessels.