resolution of all disease and other causes of death would result in a life expectation of about one hundred years. I am apprehensive about extending average life expectation beyond age one hundred once the leading killers are resolved because the result would be disease-free but nonetheless functionally weaker, still inexorably aging people….
Virtually all biomedical research has the implicit goal of eliminating disease in all of its forms. It is logical to ask what will happen if we are successful. The answer seems to be that if we are successful, our life expectation will be increased but we will eventually die from the basic aging processes that lead to failure in some vital system.
Source: “Why Do We Live as Long as We Do?” from How and Why We Age by Leonard Hayflick, PhD. Copyright ©1994 by Cell Associates, Inc. Foreword copyright © 1994 by Robert N. Butler, MD. Reprinted by permission of Leonard Hayflick, PhD.
Reading 6: Vitality and Aging
Implications of the Rectangular Curve
James F. Fries and Lawrence Crapo
Why do we age? Why do we die? How can we live longer? How can we preserve our youth? Questions about life, aging, and death are fundamental to human thought, and human beings have speculated about the answers to these questions for centuries. Our own age values the methods of science—the methods of gathering evidence, of observation, of experiment—above the musings of philosophy. Yet, philosophical speculation and scientific theory may interact and enhance each other. The scientific theories of Copernicus and the conception of a sun-centered solar system, of Newton and an orderly universe, of Einstein and the relationship between matter, energy, and spacetime, of Darwin and the evolution of species have influenced our notions of who we are, where we are, how we came to be here, and the meaning of life itself. Similarly, the study of health and aging may contribute a new philosophical perspective to these age-old questions about life and death.
The implications of new scientific discoveries are often not widely appreciated for many years. Scientific knowledge develops by small increments within a relatively cloistered scientific community, whose members are sometimes more interested in the basic ideas than in their social implications….
So it is with the study of human aging. The ancient philosophical questions have largely fallen to those who search for the biological mechanisms that affect our vitality and that cause our death. The study of aging as a separate scientific discipline is relatively new and is not yet the province of any single science. Independent observations have been made in medicine, in psychology, in molecular biology, in sociology, in anthropology, in actuarial science, and in other fields. There are remarkable parallels in the ideas that have emerged from these independent fields of research. It is our intention to review these parallel developments and to present a synthesis of scientific ideas about human aging that will offer insights into the fundamental questions about the nature and meaning of the life process, aging, and death.
The Incomplete Paradigm
The growth of scientific knowledge historically has been impeded by thought systems (paradigms) that worked well for a time but that increasingly failed to explain new observations. For the study of aging, the contemporary paradigm is often called the medical model. The medical model defines health as the absence of disease and seeks to improve health by understanding and eradicating disease. This model of life and health, while useful, has obscured a larger perspective. There are four prevalent beliefs in the medical model that have proved to be limiting (see box). Certainly, few present scholars hold these beliefs literally, but these ideas nonetheless have largely defined contemporary opinion about the aging process.
The Limiting Premises
1 The human life span is increasing.
2 Death is the result of disease.
3 Disease is best treated by medication.
4 Aging is controlled by the brain and the genes.
These four premises seem to imply the following conclusions. If the human life span is increasing, then our scientific goal can be the achievement of immortality. If death results from disease, our objective must be the elimination of disease. If disease is best treated with medication, our strategy is to seek the perfect drug or surgical procedure. With regard to aging, the medical model suggests that we should perform basic research to understand the genetic, neurologic, or hormonal mechanisms that control the process, and then learn to modify them.
Historically, these premises, objectives, and strategies have been useful. They are still worthy and deserving of study and hope. But they are certainly incomplete, and, taken literally, they are misleading. The human life span is not increasing; it has been fixed for a period of at least 100,000 years. The popular misconception of an increasing life span has arisen because the average life expectancy has increased; the life span appears to be a fixed biological constant. Three terms must be understood. The maximum life potential (MLP) is the age at death of the longest-lived member of the species—for human beings, 115 years. The life span is the age at which the average individual would die if there were no disease or accidents for human beings, about 85 years and constant for centuries. The life expectancy is the expected age at death of the average individual, granting current mortality rates from disease and accident. In the United States, this age is 78 years and rising.
Death does not require disease or accident. If all disease and all trauma were eliminated, death would still occur, at an average age not much older than at present. If premature death were eliminated, and it may be in large part, we would still face the prospect of a natural death.
Medical treatment is not the best way to approach current national health problems. The major chronic diseases (atherosclerosis, cancer, emphysema, diabetes, osteoarthritis, and cirrhosis) represent the major present health threats. They are deserving of continued medical research, and further advances are to be expected. But abundant evidence points to personal health habits as the major risk factors for these diseases. Preventive approaches now hold far more promise than do therapeutic approaches for improving human health.
Aging does not appear to be under direct control of the central nervous system or the genes. Rather, the aging process occurs in cells and in organs. The aging process is most likely an essential characteristic of biological mechanisms. The process of aging, or senescence, is an accumulation in cells and organs of deteriorating functions that begins early in adult life. Aging may result from error-prone biological processes similar to those that have led to the evolution of species.
So the prevailing ideas about aging are incomplete. An increasing body of new scientific information requires revision and extension of these ideas. The time for a new synthesis has arrived, heralded by a number of new discoveries that do not fit well into the old paradigm but that as yet lack a coherent paradigm of their own.
Competing Themes
Changes in our ideas about health and aging are now being reflected in our social institutions and lifestyles. Change in a prevalent system of thought is often turbulent, and such turbulence is now manifest in health by a set of new movements. Within the medical community, there has been increasing recognition of the importance of preventive medical approaches. Such technical strategies as mass screening have been promoted. New departments of preventive medicine have been developed within medical schools; previously, such efforts were largely carried out within schools of public health. These developments are not entirely successful (screening efforts have proved disappointing, and some departments of preventive medicine have not thrived), but
