Читать книгу Aging - Harry R. Moody - Страница 92

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.