Diabetes mellitus is one of the most prevalent chronic health problems in humans. Its prevalence increases from 10% in people < 65 years to 12% in people < 70 years, and to 15% in people over 80 years of age. People with diabetes are identified by their blood glucose levels being higher than ‘normal’. This chronic metabolic abnormality is associated with pathologic changes involving both small and large blood vessels, causing eye, kidney, and myocardial failure, as well as loss of lower limbs. A more subtle complication associated with the hyperglycemia of diabetes mellitus is cognitive dysfunction, which should be termed diabetic central neuropathy, which currently is not generally recognized. It now appears that diabetes, with resulting exposure of the brain to chronic elevated glucose levels, results in slowly evolving neurodegenerative changes. Intelligence is noted to be reduced to the lower end of the average range; psychomotor processing speed, mental flexibility and attention are specific skills that are impaired in subjects with chronic hyperglycemia. The recent recognition of a greater prevalence of silent type 2 diabetes in subjects with Alzheimer’s disease has suggested a cause and effect relationship between the two. All Individuals with Down’s syndrome are believed to develop Alzheimer’s disease. Subjects with trisomy 21 have also been observed to have elevated levels of Inositol in their brains. Laboratory animals as well as humans with chronic hyperglycemia (diabetes) have also been noted to have elevated Inositol levels in the hippocampal region of the brain.  This elevated Inositol level has been linked to increased hippocampal amylin production and deposition. Amylin aggregates may be the cause of the dendritic tangles associated with Alzheimer’s dementia. This association may be a consequence of chronic hyperglycemia that should not be overlooked when managing older patients with diabetes mellitus. Prevention of Alzheimer’s dementia should be added to the list of reasons for prescribing the best metabolic control of diabetes in all patients who have diabetes mellitus, regardless of age.