Aging and arterial structure-function relations.

Aging and hypertension interact and are associated with long-term changes in arterial structure and function. Systolic BP is not constant along the arterial tree due to different proportional contributions of forward and reflected pressure waves. Brachial cuff BP values are inadequate to detect these changes. Increased PP is the result of an imbalance between arterial flow and arterial impedance, which can be due to increased effective arterial wall stiffness or to a smaller proportional arterial diameter. After middle age, there is both dilation and stiffening of large arteries, along with increased effective stiffness caused by the corresponding changes in content of collagen, elastin, and VSM in the vascular wall. Intermediate conduit arteries also dilate with age but their functional characteristics remain relatively preserved. In the microcirculation, vasoconstriction, VSM hypertrophy and rarefaction accompany and may contribute to changes in organ function.