The most significant changes in organ reserve occur in the heart, lungs, and kidneys. The amount of reserve lost varies between people and between different organs in a single person. These changes appear slowly and over a long period of time. Even so, when an organ is worked harder than usual it may not be able to increase function. Sudden heart failure or other problems can develop when the body is worked harder than usual. Things that produce an extra workload (body stressors) include the following:
- Certain medications
- Illness
- Significant life changes
- Suddenly increased physical demands on the body, for example:
- A sudden change in activity
- Exposure to a higher altitude
Loss of reserve also makes it harder to restore equilibrium in the body. Drugs are detoxified at a slower rate. Lower doses of medications may be needed, and side effects become more common. Medication side effects can mimic the symptoms of many diseases, so it is easy to mistake a drug reaction for an illness. Some medications have entirely different side effects in the elderly than in younger people.
AGING THEORY
No one really knows how and why people change as they get older. Some theories claim that aging is caused by accumulated injuries from ultraviolet light, wear and tear on the body, by-products of metabolism, and so on. Other theories view aging as a predetermined, genetically-controlled process. However, no theory sufficiently explains all the changes of the aging process. Aging is a complex and varied process that varies in how it affects different people and even different organs. Most gerontologists (people who study aging) feel that aging is the cumulative effect of the interaction of many lifelong influences. These influences include heredity, environment, cultural influences, diet, exercise and leisure, past illnesses, and many other factors. Unlike the changes of adolescence, which are predictable to within a few years, each person ages at a unique rate. Some systems begin aging as early as age 30. Other aging processes are not common until much later. Although some changes typically occur with aging, they occur at different rates and to different extents. There is no reliable way to predict specifically how you will age.