What Is Aging? Why Do We Age?

by National Institute on Aging

The study of aging is not what it used to be. Gerontology was a young science when Congress created the National Institute on Aging (NIA) in 1974 as part of the National Institutes of Health (NIH). At that time, theories of aging abounded, but data was scant. Gerontology lacked, or was just in the early stages of developing, ways to explore the fundamentals of the aging process. Knowledge of aging clustered around specific diseases associated with advancing age; indeed the notion that aging equated with decline and illness was widespread.

Now, nearly 30 years later, the science base has grown in depth, breadth, and detail. And, with this growth have come new insights into the processes and experience of aging. Where gerontologists once looked for a single, all-encompassing theory to explain aging - a single gene, for instance, or the decline of the immune system - they are now finding multiple processes, combining and interacting on many levels. Cells, proteins, tissues, and organ systems are all involved, and gerontologists are now able to discern many more of the mechanisms by which these components cause or react to aging.

Much of this research has been supported or conducted by the NIA. In addition to research in laboratories in Baltimore and Bethesda, Maryland, the Institute sponsors basic, clinical, epidemiological, and social research on aging at universities, medical centers, and other sites worldwide. As this work evolves and new knowledge accumulates, gerontologists hope to move closer to their ultimate goal of promoting health and independence throughout the lifespan.

Posing Questions, Finding Answers

In 1965, a lawyer made an unusual deal with one of his older clients, Jeanne Calment of Arles, France. In exchange for ownership of her apartment, he agreed to pay her a monthly pension for the rest of her life. Because Mme. Calment was 90 years old at the time, it seemed likely that the lawyer would only have to make a few payments before her demise. As it turned out, however, it was a much better bargain for Mme. Calment. During the next 32 years of her extraordinary life, she was paid three times the worth of the apartment.

"We all make bad deals in life," Mme. Calment once joked to the astounded attorney. When her well documented life ended on August 4, 1997 at age 122 years 5 months and 14 days, she is believed to have lived longer than any other person in recorded history. She outlived Shigechiyo Izumi of Japan, who had held the unverified longevity record of 120 years, 237 days. She outlived her husband, who died in 1942, four years before their 50th wedding anniversary. She outlived her daughter, who died in 1936. She outlived her only grandson, who died in 1963. And yes, she outlived her lawyer who died - at age 77 - soon after Mme. Calment's 120th birthday. Long lives like Mme. Calment's are a wonder. Of the planet's current 6 billion inhabitants, perhaps no more than 25 people are more than 110 years old. So these super centenarians, as they are known, are clearly humanity's ultimate marathoners. But why? What factors allowed Jeanne Calment, who was 14 when the Eiffel Tower was completed and who once sold painting supplies to Vincent Van Gogh, to live such a long life that she herself became part of history? Is genetics the key factor? Mme. Calment's ancestors were legendary for their long lives. Is it where people live? As of 2001, ten of the world's oldest people were Japanese, six were American, three were French, and two were Italian. Is there something special about how these people live? Mme. Calment took up fencing lessons at 85, still rode a bicycle at age 100, smoked until she was 117, and ate a diet rich in olive oil all of her life. In truth, there probably is no single "secret" of aging. More than likely, all of these elements - heredity, environment, and lifestyle - have complex roles in determining whether an individual will have a long and healthy life, according to scientists who study aging.

These scientists, called gerontologists, ponder other fundamental questions. Why do we age? What happens as we age? Why do some people age faster or slower and in different ways than others? Is there a maximum human lifespan beyond which we cannot live no matter how optimal our environment or favorable our genes? And finally for all of us, the most important question: How can insights into longevity be used to fight the diseases and disabilities associated with old age to make sure this period of life is healthy, active, and independent?

Researchers at the National Institute on Aging (NIA), part of the National Institutes of Health, are seeking answers to these and other important questions. Established by the Federal Government in 1974, the NIA conducts and supports research on aging and educates the public about its findings.

Aging Under the Microscope: A Biological Quest describes what we know so far about the answers to these questions. It offers an overview of research on aging and longevity, describing the major puzzle pieces already in place and, to the extent possible, the shapes of those that are missing.

What Is Aging? What Is Senescence?

Aging is a complex natural process potentially involving every molecule, cell, and organ in the body. In its broadest sense, aging merely refers to changes that occur during the lifespan. However, this definition includes some changes that aren't necessarily problematic, and usually don't affect an individual's viability. Gray hair and wrinkles, for instance, certainly are manifestations of aging, but neither is harmful.

To differentiate these superficial changes from those that increase the risk of disease, disability, or death, gerontologists prefer to use a more precise term - senescence - to describe aging. Senescence is the progressive deterioration of many bodily functions over time. This loss of function is accompanied by decreased fertility and increased risk of mortality as an individual gets older. The rate and progression of this process can vary greatly from person to person, but generally over time every major organ of the body is affected. As we age, for instance, lung tissue loses much of its elasticity, and the muscles of the rib cage shrink. As a result, maximum vital breathing capacity progressively diminishes in each decade of life, beginning at about age 20. With age, blood vessels accumulate fatty deposits and lose much of their flexibility, resulting in arteriosclerosis or "hardening of the arteries." In the gastrointestinal system, production of digestive enzymes diminishes, and as a result, tissues lose much of their ability to break down and absorb foods properly. In women, vaginal fluid production decreases and sexual tissues atrophy with increasing age. In men, sperm production decreases and the prostate enlarges.

About the Author

www.nia.nih.gov
NIA, one of the 27 Institutes and Centers of NIH, leads a broad scientific effort to understand the nature of aging and to extend the healthy, active years of life. In 1974, Congress granted authority to form NIA to provide leadership in aging research, training, health information dissemination, and other programs relevant to aging and older people.