Physiologic Changes of Aging

After completing this section of the chapter, you should be able to meet the following objectives:

♦ Describe common skin changes that occur with aging

♦ Explain how muscle changes that occur with aging affect
high-speed performance and endurance

♦ Describe the process of bone loss that occurs with aging

♦ State the common changes in blood pressure regulation
that occur with aging

♦ List the changes in respiratory function that occur with
aging

♦ Relate aging changes in neural function to the overall
function of the body

♦ Briefly discuss the effects of aging on vision, hearing,
taste, and smell

♦ Describe three changes that occur in the gastrointestinal
tract with aging

♦ State the significance of decreased lean body mass on
interpretation of the glomerular filtration rate using
serum creatinine levels

The physiologic changes seen in the elderly reflect not only the aging process but also the effects of years of expo­sure to environmental agents, such as sunlight and cigarette smoke, and disease processes such as diabetes mellitus. Overall, there is a general decline in the structure and func­tion of the body with advancing age. The decline results in a decreased reserve capacity of the various organ systems that consequently produce reduced homeostatic capabili­ties, making the older adult more vulnerable to stressors such as illness, trauma, surgery, medications, and environ­mental changes.

Research to identify true age-related changes as opposed to disease states is difficult. Studies using cross-sectional methodologies are the easiest to perform; however, mor­tality can confound the results. Although longitudinal studies tend to be more precise, they require years to perform and may not be able to account for numerous variables that enter into the aging equation, such as envi­ronment, occupation, and diet. However, it is important to differentiate, as much as possible, those changes that occur in the body as a result of aging from those that occur because of disease. This distinction allows for more accu­rate diagnosis and treatment of disease conditions and helps to avoid inappropriate labeling of aging changes.

Regardless of the difficulty in defining normal aging as it relates to the various organ systems, there is a pat­tern of gradual loss that occurs. Many of these losses be­gin in early adulthood, but because of the large physiologic reserve of most organ systems, the decrement does not become functionally significant until the loss reaches a certain level. Some changes, such as those that affect the skin and posture, are more visible, whereas others, such as those affecting the kidney, may go unnoticed until the person is challenged with situations such as metabolizing and eliminating medications.