Concepts of Health and Disease
arly peoples were considered long-lived if they reached 30 years of age—that is, if they survived infancy. For many centuries, infant mortality was so great that large families became the tradition; many children in a family ensured that at least some would survive. Life expectancy has increased over the centuries, and today an individual in a developed country can expect to live about 71 to 79 years. Although life expectancy has increased radically since ancient times, human longevity has remained fundamentally unchanged. The quest to solve the mystery of human longevity, which appears to be genetically programmed, began with Gregor Mendel (1822–1884), an Augustinian monk. Mendel laid the foundation of modern genetics with the pea experiments he performed in a monastery garden. Today, geneticists search for the determinant, or determinants, of the human life span. Up to this time, scientists have failed to identify an aging gene that would account for a limited life span. However, they have found that cells have a ﬁnite reproductive capacity. As they age, genes are increasingly unable to perform their functions. The cells become poorer and poorer at making the substances they need for their own special tasks or even for their own maintenance. Free radicals, mutation in a cell’s DNA, and the process of programmed cell death are some of the factors that work together to affect a cell’s functioning.
Concepts of Health and Disease
Georgianne H. Heymann Carol M. Porth
ogy. There has been an increased knowledge of immune mechanisms; the discovery of antibiotics to cure infections; and the development of vaccines to prevent disease, chemotherapy to attack cancers, and drugs to control the manifestations of mental illness. The introduction of the birth control pill and improved prenatal care have led to decreased birth rates and declines in infant and child mortality. The beneﬁts of science and technology also have increased the survival of infants born prematurely and of children with previously untreatable illnesses, such as immunodeﬁciency states and leukemia. There also has been an increase in the survival of very seriously ill and critically injured persons of all age groups. Consequently, there has been an increase in longevity, a shift in the age distribution of the population, and an increase in age-related diseases. Coronary heart disease, stroke, and cancer have now replaced pneumonia, tuberculosis, and diarrhea and enteritis—the leading causes of death in the 1900s. This chapter, which is intended to serve as an introduction to the book, is organized into four sections: health and society, historical perspectives on health and disease, perspectives on health and disease in individuals, and perspectives on health and disease in populations. The chapter is intended to provide the reader with the ability to view within a larger framework the historical aspects of health and disease and the relationship of health and disease to individuals and populations, and to introduce the reader to terms, such as etiology and pathogenesis, that are used throughout this text.
HEALTH AND SOCIETY HEALTH AND DISEASE: A HISTORICAL PERSPECTIVE The Inﬂuence of Early Scholars The Nineteenth Century The Twentieth Century The Twenty-First Century PERSPECTIVES ON HEALTH AND DISEASE IN INDIVIDUALS Health Health and Disease as States of Adaptation Disease Etiology Pathogenesis Morphology Clinical Manifestations Diagnosis Clinical Course PERSPECTIVES ON HEALTH AND DISEASE IN POPULATIONS Epidemiology and Patterns of Disease Prevalence and Incidence Morbidity and Mortality Determination of Risk Factors The Framingham Study The Nurses’ Health Study Natural History Levels of Prevention Evidence-Based Practice and Practice Guidelines
he concepts of what constituted health and disease at the beginning of the last century were far different from those of this century. In most...