PREVIEW Aging is a gradual, continuous process of natural change that begins in early adulthood. During early middle age, many bodily functions begin to gradually decline. 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. Many years ago, age 65 was chosen as the age for retirement in Germany, the first nation to establish a retirement program. In 1965 in the United States, age 65 was designated as the eligibility age for Medicare insurance. This age is close to the actual retirement age of most people in economically advanced societies. When a person becomes old can be answered in different ways: Chronologic age is based solely on the passage of time. It is a person's age in years. Chronologic age has limited significance in terms of health. Nonetheless, the likelihood of developing a health problem increases as people age, and it is health problems, rather than normal aging, that are the primary cause of functional loss during old age. Because chronologic age helps predict many health problems, it has some legal and financial uses. Biologic age refers to changes in the body that commonly occur as people age. Because these changes affect some people sooner than others, some people are biologically old at 65, and others not until a decade or more later. However, most noticeable differences in apparent age among people of similar chronologic age are caused by lifestyle, habit, and subtle effects of disease rather than by differences in actual aging. Psychologic age is based on how people act and feel. For example, an 80-year-old who works, plans, looks forward to future events, and participates in many activities is considered psychologically younger. Most healthy and active people do not need the expertise of a geriatrician (a doctor who specializes in the care of older people) until they are 70, 75, or even 80 years old. However, some people need to see a geriatrician at a younger chronologic age because of their medical conditions. Oder a copy now!