Type 2 diabetes is becoming increasingly common in most Westernized countries and it now occurs at a younger age. There are pathologies associated with diabetes, mostly systemic ones. However, a growing number of studies is also showing that diabetes is associated with impaired cognitive processes in older adults and hasten the progression to dementia. The most common cognitive deficits are decreases in processing speed and verbal memory; these may extend to other aspects of cognition with increasing age. The link between diabetes and cognitive decline is obscured by depression, hypertension, as well as cardio- and cerebrovascular diseases, all of which occur to varying degrees in diabetic patients. A few studies indicate that controlling blood glucose with anti-diabetic treatments may help prevent the cognitive decline in diabetic patients before they are 70 years old. After that age, diabetes appears to produce faster cognitive decline and may increase the occurrence of pathological changes associated with vascular dementia or Alzheimer's disease.