Cells are the basic building blocks of tissues. All cells experience changes with aging. They become larger and are less able to divide and reproduce. Among other changes, there is an increase in pigments and fatty substances inside the cell (lipids). Many cells lose their ability to function, or they begin to function abnormally.
Waste products accumulate in tissue with aging. A fatty brown pigment called lipofuscin collects in many tissues, as do other fatty substances.
Connective tissue changes, becoming increasingly stiff. This makes the organs, blood vessels, and airways more rigid. Cell membranes change, so many tissues have more trouble receiving oxygen and nutrients and getting rid of carbon dioxide and wastes.
Many tissues lose mass. This process is called atrophy. Some tissues become lumpy (nodular) or more rigid.
Because of cell and tissue changes, your organs also change as you age. Aging organs gradually but progressively lose function, and there is a decrease in the maximum functioning capacity. Most people do not notice this loss, because you seldom need to use your organs to their fullest capability.
Organs have a "reserve," an ability to function beyond the usual needs. For example, the heart of a 20-year-old is capable of pumping about 10 times the amount that is actually needed to preserve life. After age 30, an average of 1% of this reserve is lost each year.
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:
Loss of reserve also makes it harder to restore equilibrium in the body. Drugs are detoxified at a slower rate. So 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.
