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Aging is a gradual, continuous process of spontaneous change that begins at birth and continues throughout all stages of life. It involves maturation and development for children, adolescents, and young adults. Then, during middle and late age, many bodily functions decline. Thus, aging has positive and negative aspects.
People do not become old or elderly at any specific age. Traditionally, age 65 has been designated as the beginning of old age. But the reason was based in history, not biology. Age 65 was chosen as the age for retirement in Germany, the first nation to establish a retirement program, and it continues to be the retirement age for most people in developed societies, although this tradition is changing.
When a person becomes old can be answered in different ways:
Normal Aging:
People often wonder whether what they are experiencing as they age is normal or abnormal. Although people age somewhat differently, many changes occur in almost everyone. Some of these changes seem to result from internal processes, that is, from aging itself. Thus, such changes, although undesired, are considered normal. They are to be expected and are generally unavoidable. For example, as people age, the lens of the eye thickens, stiffens, and becomes less able to focus on close objects, such as reading materials (a disorder called presbyopia). This change occurs in virtually all older people, and no cause or explanation has been identified other than aging itself. Thus, presbyopia is considered normal aging. Other terms used to describe these changes are usual aging and senescence.
Exactly what constitutes normal aging is not always exactly clear. Changes that occur with normal aging make people more likely to develop certain disorders. However, people can sometimes take actions to compensate for these changes. For example, older people are more likely to lose teeth. But seeing a dentist regularly, eating fewer sweets, and brushing and flossing regularly may reduce the chances of tooth loss. Thus, tooth loss, although common with aging, may be an avoidable part of aging.
Also, sometimes functional decline that is part of aging may seem similar to functional decline that is part of a disorder. For example, with advanced age, a decline in mental function is nearly universal and is considered normal aging. This decline includes increased difficulty learning new languages and increased forgetfulness. In contrast, the decline that occurs in dementia is much more severe. For example, people who are aging normally may misplace things or forget details, but people who have dementia may forget entire events. People with dementia also have difficulty doing normal daily tasks (such as driving, cooking, and handling finances) and understanding the environment, including knowing what year it is and where they are. Thus, dementia is considered a disorder, even though it is common in late life (see Delirium and Dementia). Certain kinds of dementia, such as Alzheimer's disease, differ from normal aging in other ways as well. For example, brain tissue (obtained during autopsy) in people with Alzheimer's disease looks different from that in older people without the disease. So the distinction between normal aging and dementia is clear.
Sometimes the distinction between functional decline that is part of aging and functional decline that is part of a disorder seems arbitrary. For example, as people age, blood sugar levels increase more after eating carbohydrates than they do in younger people. This increase is considered normal aging. However, if the increase exceeds a certain level, diabetes, a disorder, is diagnosed (see Diabetes Mellitus (DM)). In this case, the difference is one of degree only.
Healthy
(Successful) Aging:
Healthy aging refers to postponement of or reduction in the undesired effects of aging. The goals of healthy aging are maintaining physical and mental health, avoiding disorders, and remaining active and independent. For most people, maintaining general good health requires more effort as they age. Developing certain healthy habits—following a nutritious diet, exercising regularly, and staying mentally active—can help. The sooner a person develops them, the better. However, it is never too late to begin. In this way, people can have some control over what happens to them as they age.
Some evidence suggests that in the United States, healthy aging is on the rise:
Life
Expectancy
The average life expectancy of Americans has been increasing dramatically over the past century. A male child born in 1900 could expect to live only 46 years, and a female child, 48 years. Today, however, a male child can expect to live more than 73 years, and a female child, nearly 80 years. Although much of this gain can be attributed to the significant decrease in childhood mortality, life expectancy at every age beyond 40 has also increased dramatically. For example, a 70-year-old man can now expect to live beyond age 83, and a 70-year-old woman, beyond age 85.
Despite the increase in average life expectancy, the maximum life span—the oldest age to which people can live—has changed little since records have been kept. Despite the best genetic makeup and health care, no one seems to live much beyond 125 years, although some experts suggest that this number may be slowly increasing. Currently, a person has a 1 in 2 billion chance of living to the age of 120.
Several factors influence life expectancy:
Last full review/revision August 2007 by Richard W. Besdine, MD
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