http://www.merck.com/pubs/mmanual_ha/contents.html
- Fundamentals of Aging
- Caring for Self and Others
- Medical Conditions
- Social, Legal, and Ethical Issues
- Essays
Excerpt from the Section 1:
When Does a Person Become Old?
When Does a Person Become Old?
The traditional designation for old age—65 years—has no basis in biology. Many people are vigorous and active at 65. Others are sick and inactive at 40. Rather, the basis for choosing age 65 is in history. Age 65 was chosen as the age for retirement in Germany, the first nation to establish a retirement program. (In 1889, Bismarck, Germany's Chancellor, first chose age 70, but in 1916, the age was lowered to 65.)
The question as to 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. Because chronologic age helps predict many health problems, it has some legal and financial uses. It is also used to determine eligibility for some programs for older people.
Biological age refers to changes in the body that commonly occur as people age. For example, vision and hearing typically worsen as people age. Because these changes affect some people more than others, some people are biologically old at 40, and others are biologically young at 60 and even older.
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 young. Such a person is commonly described as "being young at heart."
