ABSTRACT
Aging is difficult to define but is perhaps most widely understood to be a decrease in the ability to survive. As people age (Figure 18.1), they are less able to perform strenuous physical activities which were relatively easy when they were younger. With aging comes a decline in the function of most organs in the body, making elderly people more susceptible to disease. Indeed, most major diseases of the developed world, such as coronary heart disease (Chapter 14), cancer (Chapter 17), and diabetes type 2 (Chapter 7) are age-related. With aging comes senescence, that is, a decline in functions of almost all parts of the body and at all levels of organization, from cells to organ systems. Senescence changes may be responsible for some disease of old age or may increase susceptibility to certain diseases. Thus elderly people make up a large proportion of patients in hospitals and in most countries a high proportion of the health budget is devoted to the care and treatment of the elderly.
