Aging is a process we all face, though some see signs faster than others.  And while most people focus on their appearance, changes at the cellular level are critical to our health and are of particular interest to scientists tackling the question of why we age. One way researchers are learning about the process is by studying a condition called progeria, a rare genetic condition that causes rapid aging in children.

How do cells age?

Cells in our body have different responsibilities. Some are constantly reproducing, such as those in the gastrointestinal tract;  others are capable of reproducing, if damaged, such as those inside the arteries, and still others cannot reproduce at all, such as nerves, the heart and muscles.

The four basic types of tissue in our body include: connective tissue, which supports other tissues and binds them together (bone, blood, lymph tissues); epithelial tissue, a lining for passages inside the body (gastrointestinal system); muscle tissue, which moves the skeleton (also smooth muscle and cardiac muscle); and nerve tissue, which is made up of neurons carrying messages to different parts of the body (brain and spinal cord).

As these types of tissue age, different changes take place. All aging cells become larger and less able to divide and multiply. There also is an increase in cell lipids and pigments, and a buildup of waste products begins to occur. Cells start to lose their ability to function, or they don’t function properly. Connective tissue will become stiff, which makes the organs, blood vessels and airways also less flexible. Cell membranes will have trouble getting oxygen and nutrients, and tissues will begin to lose mass.

Because of these cell changes, organs will also begin to change with age.  They slowly lose function, but generally we don’t notice.   The biggest changes occur in the heart, lungs and kidneys, but how much they change depends on the individual. This makes it harder for the body to restore balance, and overtaxed organs may cause problems, such as heart failure. Because the aging process is complicated, it’s hard to know which changes are a result of aging and which are due to medical problems.

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Why do we age?

There are several theories as to why we age, though none is definitive. One theory suggests we age from injuries over time from ultraviolet light, normal wear and tear on the body and by-products of metabolism.  Another suggests overuse of your organs through a poor diet and excessive consumption of alcohol, drugs or cigarettes can cause irreparable damage to the body.  Yet another theory suggests that aging is predetermined by your DNA, and the process is controlled by your genes. But most gerontologists believe that aging is due to the interaction of several influences, including heredity, environment, culture, diet, exercise, and past illnesses. The interesting thing about aging is that it occurs at different rates in the body and among people. There is just no way to predict how an individual will age.