As the aging process begins after maturation, deteriorative, regenerative, and compensatory changes develop over time and result in diminished physiological reserve capacity and an increased vulnerability to challenges, particular disease, and, as a result, a decrease in the ability to survive. Importantly, aging itself does not result in disease; however, it does lower the threshold for the development of disease and can intensify and accelerate the effects of disease once initiated. The increased vulnerability with age to external or internal challenges is one of the tenets of geriatrics and gerontology and is called homeostenosis.
These concepts are particularly relevant to aging of the human cardiovascular system, especially older persons living in developed countries. In these populations, it is particularly important to screen for clinical and subclinical disease, particularly atherosclerosis, as well as to consider other cultural and environmental factors that are distinct from aging yet can mimic aging effects. These can manifest in human populations studies as cohort and period effects, can be subtle or overt, and are easily confused with aging. It has been proposed that a true age-related change should be absent in young persons, increase with age, be universally present in very old persons, and not be related to any known, definable disease.
In some early human aging studies, subjects with clinical and subclinical disease were not excluded, leading to an overestimation of the effects of aging on the cardiovascular system. Coronary atherosclerosis is highly prevalent in western societies and is one of the important disorders that can be occult and can significantly affect cardiac function. Systemic arterial hypertension is even more common. Therefore, reasonable screening for these two most common disorders is prudent to separate aging from disease.
In addition to the effects of subclinical disease, there are additional effects of physical inactivity. Humans and many animals become increasingly sedentary as they age. For example, rats given free access to a running wheel will run 20 km per week when they are young, but this decreases to less than 7 km per week when approaching the age of 23 months. Many older people are even less active. Another increasingly important life-style-related factor relatively new to civilization is obesity. Adipose tissue owing to excess caloric intake has numerous effects involving nearly all physiological systems, including cardiovascular, and obesity increases substantially with age. Thus, the changes that are seen in an older population reflect the combination of all these factors, period, cohort, lifestyle, and disease-related changes, as well as the biological effect of age itself. It is often challenging to precisely separate and discern, both qualitatively and quantitatively, the latter from the former. However, awareness of the important nuances of normal aging can help avoid most errors.
Age Changes in Arterial Structure
With age a number of ultrastructural changes occur in the aorta, and all appear to contribute to increased stiffness. Elastin becomes fragmented in the internal elastic lamina ...