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Health A-Z

Medical Content Created by the Faculty of the
Harvard Medical School

What Is It?

The thought of aging conjures some common perceptions: wrinkles, gray hair, a slightly stooped posture, perhaps some "senior moments" of forgetfulness. In fact, the process of aging has a nearly universal impact on our bodies, affecting our cells, tissues, organs, and body systems. The effects of aging can be seen in everything from our vital signs (like blood pressure) to our skin, to our bone and joints, to our cardiovascular, digestive, and nervous systems, and beyond. Some aging changes begin early in life. For example, your metabolism starts to gradually decline beginning at about age 20. Changes in your hearing, on the other hand, do not usually begin until age 50 or later.

We do not yet fully understand the complex interplay of factors that cause us to age as we do. Most likely, the vast and varied changes associated with aging result from a lifetime of environmental and cultural influences, as well as genetics, diet, exercise, illness, and a host of other factors, all of which contribute to the aging process.

A series of remarkable biological research studies since the 1990's have identified genes that can profoundly influence the rate at which cells, and animals, age. The good news from these studies is that biological changes that extend life also seem to extend vitality: animals that live longer remain quite healthy for most of their lengthened life. None of these discoveries is close to providing a "fountain of youth" for humans, but some scientists believe that research breakthroughs regarding aging in the 21st Century will lead to the development of drugs that can extend human life and simultaneously improve human health.

Following are examples of how aging affects some of our major body systems.

Cells, organs and tissues:

  • Cells become less able to divide

  • The telomeres—the ends of the chromosomes inside every cell—gradually get shorter until, finally, they get so short that the cell dies

  • Waste products accumulate in tissue

  • Connective tissue between the cells becomes stiffer

  • The maximum functional capacity of many organs decreases

Heart and blood vessels:

  • The wall of the heart gets thicker

  • Heart muscle become less efficient (working harder to pump the same amount of blood)

  • The aorta (the body's main artery) becomes thicker, stiffer, and less flexible

  • Many of the body's arteries, including arteries supplying blood to the heart and brain, slowly develop atherosclerosis, although the condition never becomes severe in some people

Vital signs:

  • It is harder for the body to control its temperature

  • Heart rate takes longer to return to normal after exercise

Bones, muscles, joints:

  • Bones become thinner and less strong

  • Joints become stiffer and less flexible

  • The cartilage and bone in joints starts to weaken

  • Muscle tissue becomes less bulky and less strong

Digestive system:

  • The movement of food through the digestive system becomes slower

  • The stomach, liver, pancreas, and small intestine make smaller amounts of digestive juices

Brain and nervous system:

  • The number of nerve cells in the brain and spinal cord decreases.

  • The number of connections between nerve cells decreases

  • Abnormal structures, known as plaques and tangles, may form in the brain.

Eyes and Ears:

  • The retinas get thinner, the irises get stiffer

  • The lenses become less clear

  • The walls of the ear canal get thinner

  • The eardrums get thicker

Skin, nails, and hair:

  • Skin gets thinner and becomes less elastic

  • Sweat glands produce less sweat

  • Nails grow more slowly

  • Hairs get gray and some no longer grow

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From Health A-Z, Harvard Health Publications. Copyright 2007 by the President and Fellows of Harvard College. All rights reserved. Written permission is required to reproduce, in any manner, in whole or in part, the material contained herein. To make a reprint request, contact Harvard Health Publications. Used with permission of StayWell.

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