Impact of aging on the body's vascular system

In this review, the effect of aging on the body's vascular system is considered in terms of potential mechanisms involved in target organ damage. First, the effects of aging on body fluid compartments, including changes that occur in subdivisions of the interstitial space (quite heterogeneous among organs), are described, with particular reference to the macromolecular composition of the fluid compartments. Second, the structure and function of different segments of the vascular system during aging are examined, with emphasis on: (1) large arterial conduits responsible for isolated systolic hypertension; (2) arteries most responsible for peripheral resistance (the "resistance arteries"); (3) microcirculation networks, including the vasa vasorum; and (4) large collecting veins that can have such an important effect on the cardiac output. Third, a detailed discussion is provided of the heterogeneous macromolecular composition of interstitial fluid compartments that are involved in the critical traffic of vital substrates, including pharmacologic agents, in transit from the systemic circulation to the various organs. The strategic position of interstitial fluid compartments, situated as they are between microcirculation networks and vital organs, is considered to be critically involved in the morbidity and mortality caused by the vascular diseases afflicting elderly persons. Finally, with respect to "physiological" and/or "morbid" aging, a re-examination is undertaken of the target organ damage observed in elderly individuals who suffer from isolated systolic hypertension, type II diabetes mellitus, peripheral vascular disease, chronic heart failure, and renal failure. Potentially new and noninvasive approaches available to clinicians for early detection of large artery rigidity are considered, along with the possible benefits of nonpharmacologic and/or pharmacologic interventions.