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Aging changes in immunity


Aging is not synonymous with illness. However, getting older does increase the risk for many diseases and disorders. Overall, elderly people have an increased rate of chronic disorders, arteriosclerosis , infections, autoimmune disorders , and cancer .

This increased risk may be caused, in part, by the nature of these disorders. Most of the chronic disorders such as arteriosclerosis are slowly progressive and do not show symptoms until they have been progressing for years.

Another significant part of this increased risk is probably related to aging changes in the immune system. The immune system protects against diseases. It seeks out and destroys viruses, bacteria, fungi, and cancerous cells before they can damage the body. It learns to tell the difference between "self" tissue and "non-self" particles.

The thymus, one of the organs of the immune system, is the site where certain immune cells called T lymphocytes or T cells mature. The thymus begins to shrink (atrophy) after adolescence. By middle age it is only about 15% of its maximum size.

Some of the T cells directly kill foreign particles. Others help coordinate other parts of the immune system, which are specialized to attack different types of infections.

Although the number of T cells does not decrease with aging, T cell function decreases. This causes a weakening of the parts of the immune system controlled by these T cells.

There is a slow, steady decrease in immunity after young adulthood. When the body is exposed to bacteria or other microorganisms (by an actual exposure or by immunization), fewer protective antibodies may be formed or they may be formed at a slower rate.

Flu shots or other immunizations may be less effective, and protection may not last as long as expected.

Later in life, the immune system also seems to become less tolerant of the body's own cells. Sometimes an autoimmune disorder develops -- normal tissue is mistaken for non-self tissue, and immune cells attack certain organs or tissues.

The immune system becomes less able to detect malignant cells, and cancer risk also increases with age as a result.

The immune system also becomes less able to detect foreign particles, and infection risk is greater.

Other things also increase the risk of infections. Sensation changes, gait changes , changes in the skin structure, and other "normal aging changes" increase the risk of injury in which bacteria can enter broken skin. Illness or surgery can further weaken the immune system, making the body more susceptible to subsequent infections. Diabetes, which is also more prevalent with age, can also lead to decreased immunity.

Besides slightly decreasing immunity, aging also affects inflammation and wound healing. Inflammation is an immune response -- when the immune system thinks there is trouble, it sends more cells to the site of the problem and this causes swelling, pain, redness, warmth and irritation, which are the hallmarks of inflammation. Inflammation often indicates infection, but may also occur due to autoimmune attack on "self" tissue as well.

Many older people heal more slowly. This may be directly related to changes in the immune system, or it may be a consequence of other problems such as diabetes or arteriosclerosis , which leads to decreased blood flow to some parts of the body such as the lower extremities.

Also, many older people take anti-inflammatory medications (to control conditions such as arthritis ) and these are also known to slow wound healing.


  • Increased infection risk
  • Decreased ability to fight diseases
  • Slowed wound healing
  • Autoimmune disorders
  • Cancer

Just as routine immunizations are important to prevent illness in children, a few routine immunizations are important as we get older. Adult tetanus (Td) immunizations should be given every 10 years (a booster may be given sooner if there is a "dirty" wound).

Your health care provider may recommend other immunizations, including pneumovax (to prevent pneumonia or its complications), flu vaccine , hepatitis immunization, or others. These optional immunizations are not necessary for ALL older people, but are appropriate for some.

Keeping generally healthy also helps. Maintaining good health involves the following:

  • Exercise.
  • Eat a well-balanced diet .
  • Stop smoking.
  • Minimize alcohol use . Moderate drinking seems to have some health benefits, but excessive drinking can cause serious damage.
  • Use safety measures to avoid falls and other injuries.


  • Aging changes in hormone production
  • Aging changes in organs, tissues, and cells

Update Date: 12/23/2002

Steven Angelo, M.D., Assistant Professor of Medicine, Yale School of Medicine, New Haven, CT. Review provided by VeriMed Healthcare Network.

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Last updated: Tue, 06 Jan 2009 00:20:03 GMT