Diabetic patients are more likely to manifest impaired cognitive function, cognitive decline and a significantly higher risk of developing Alzheimer's disease or vascular dementia. Both hyperglycaemia and insulin resistance (IR) have also been shown in population-based studies to be associated with poor cognitive function in older persons. Hippocampal volumes were smaller in diabetic patients and in those with increased insulin resistance than in normal healthy controls. Several mechanisms are likely to explain the increased risk of cognitive impairment in T2D. Insulin resistance as mentioned above has been shown to play a direct role in cognitive impairment in individuals with type 2 diabetes (T2D). Additionally, chronic hyperglycaemia has been shown to be associated with decreased cerebral blood flow, decreased glucose transport across the blood brain barrier, reduced cerebral glucose metabolism and microvascular changes from endothelial damage. Finally, metabolic and vascular risk factors such as dyslipidaemia and hypertension which are closely linked to IR and T2D have been shown to predict cerebrovascular disease, cognitive decline and dementia.