Linking cerebrovascular defense mechanisms in brain ageing and Alzheimer's disease.

Apart from the cardiovascular system, several cerebrovascular defense mechanisms inherently function to maintain homeostasis of the neurovascular unit. Prevailing evidence suggests that cerebrovascular functions decline differentially during normal ageing with pronounced effects in Alzheimer's disease (AD). This commentary highlights how vascular regulatory mechanisms may change with age and precede disease to explain the interesting links between changes in the cerebral endothelium, cerebral blood flow (CBF) and functional hyperemia during ageing that are already apparent in AD.