Diabetes mellitus (DM2) and Alzheimer's disease (AD) are both more prevalent with aging, but it has generally been assumed that this is coincidental, not a reflection of co-morbidity. However, evidence suggests that patients with T2DM are at an increased risk of getting Alzheimer's disease and that hyperinsulinemia and insulin resistance – hallmarks of DM2 can lead to memory impairment. Inadequate glucose control leads to medical complications and, possibly through defective leptin signaling, includes effects on the central nervous system (CNS). Diabetes affects the blood vessels and nerves of the body and causes long-term complications. Many people with diabetes have brain changes that are hallmarks of Alzheimer's disease. Epidemiological and biological evidence supports a link between these two aging-related diseases. First and foremost, diabetes mellitus is associated with changes in cognition and cognitive dysfunction. Persons with diabetes have been reported to hold a higher incidence of cognitive decline and AD; DM2 has been strongly associated with an increased risk of developing all types of dementia, including Alzheimer's disease.