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Chapter 14

Aging can be defined as the accumulation of diverse adverse changes that increase the risk of death.1 These aging changes are responsible for both the commonly recognized sequential alterations that accompany advancing age beyond the early period of life, and the progressive increases in the chance of disease and death associated with them.1

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 Geriatrics is the branch of medicine that focuses on health promotion and the prevention and treatment of disease and disability in later life.Gerontology is the study of the aging process and the science related to the care of the elderly.

The changes associated with aging can be attributed to a combination of development, genetic defects, the environment, disease, and an innate factor, the aging process. The rate of aging, that is, the rate of production of aging changes, normally varies from individual to individual, due to differences in genetic and environmental factors that modulate production of aging changes, and thus contribute to differences in the age of death and of the onset of disease.1 A wide array of theories exist as to why aging occurs, why species have the life spans they do, and what kinds of factors are likely to influence the aging process. For example, the aging process has been attributed to the following:

• Molecular cross-linking (Glycosylation).2-4 Glycosylation involves the abnormal process of the binding of glucose (simple sugar) to protein, a process that requires oxygen. Once this binding has occurred, the protein becomes impaired and is unable to perform as efficiently. Examples of known cross-linking disorders include senile cataract and the appearance of tough, leathery and yellow skin.
• Changes in immunologic function (neuroendocrine-immuno theory).5-8 The immune system is the most important line of defense against foreign substances that enter the body. With age the system's ability to produce necessary antibodies that fight disease declines, as does its ability to distinguish between antibodies and proteins. In a sense the immune system itself becomes self-destructive and reacts against itself. Examples of autoimmune disease are lupus, scleroderma and adult-onset diabetes.
• Damage by free-radical reactions.9 The term free radical describes any molecule that has a free electron. Theoretically, this free electron reacts with healthy molecules in a destructive way by creating an extra negative charge. This unbalanced energy makes the free radical bind itself to another balanced molecule as it tries to steal electrons. In so doing, the balanced molecule becomes unbalanced and transforms into a free radical itself. It is known that diet, lifestyle, drugs (eg, tobacco and alcohol) and radiation etc, are all accelerators of free radical production within the body. However, there is also natural production of free radicals within the body as a byproduct of energy production, particularly from the mitochondria.
• Senescence genes in the DNA (planned obsolescence).1 The planned-obsolescence theory focuses on the genetic programming encoded within the DNA, the blueprint ...

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