Epidemiology Foundations

The Science of Public Health

Peter J. Fos

• Éditeur: Jossey-Bass
• Année: 2010
• ISBN:
  9780470910726
• Édition: 1
• Sujet: Médecine
• Sous-sujet: Biostatistiques

Written by Peter J. Fos—an expert in epidemiology with more than twenty years teaching experience—Epidemiology Foundations offers an ideal introduction to the theory and practice of public health epidemiology. This important text discusses both the historical perspective and future trends of epidemiology, reviews health and disease, and explains how they are measured. The book's overview of epidemiological studies shows how they are used in practice. Epidemiology Foundations takes a social and community perspective and includes information about global diseases and epidemics.

Emphasis on concepts such as population health, social determinants, and global health make this book especially interesting and accessible to those new to the subject. Each chapter is supplemented with problem-solving exercises and research assignments to aid readers in understanding its epidemiology principles. Reflecting and expanding on recommendations of the Association of American Colleges and Universities, Epidemiology Foundations is the ideal text for any course introducing epidemiology in public health.

CHAPTER 1

WHY EPIDEMIOLOGY?

LEARNING OBJECTIVES

On completing this chapter, you will be able to

Define epidemiology

Discuss the concept of populations and population health

Describe population trends and characteristics

Describe global health threats

Discuss the relationship and distinction between public health and medicine

Introduction 2

Public Health and Community Medicine 2

Definition of Epidemiology 3

Population Health 9

Population Trends 10

Health Costs 15

Global Health Threats 17

Summary 17

Introduction

Epidemiology is, for most, a word that seems to be from another language. It is certainly not a word we use in everyday conversation. But epidemiology is a science that affects all of us every day of our lives. We shop for food each day with little regard to or worry about whether what we purchase and eat is unsafe. For many of us, smallpox, polio, plague, diphtheria, yellow fever, and cholera are diseases that either we have never heard of or we do not give much thought or attention to. Human immunodeficiency virus (HIV) infection and acquired immunodeficiency syndrome (AIDS) are diseases that are well known, but they are becoming less of a daily concern. New, so-called emerging diseases such as bird flu are now garnering a great deal of our attention.

Public Health and Community Medicine

Before continuing the discussion on “why epidemiology,” the concept of public health must be explained further. Public health is the science and practice of protecting and improving the health of a community. This can be done with preventive medicine, health education, the control of communicable diseases, the use of sanitary measures, and the monitoring of environmental conditions. Public health is concerned with the health of the community as a whole. In other words, public health and community health are synonymous.

Public health is focused on three areas: assessment and monitoring of health and disease, development of public health policies that assist in addressing health problems, and allowing for access to public health care services. These public health care services include disease prevention, health education, and health promotion. Often public health services are considered to be the same as medical care services because of the assumed similarities. The distinction is that public health services are focused on populations, not individuals. It is true that populations are made up of individuals, so public health acknowledges the importance of the welfare of individuals, but the focus of services is on larger populations. Public health services are centered on diagnosing and monitoring health issues and providing health education and health promotion services to communities.

An example of this communitywide perspective of public health is considered an accomplishment. Public health is concerned with immunization for preventable disease, such as smallpox, poliomyelitis, measles, rubella, tetanus, diphtheria, and Haemophilus influenzae type b. Since immunization programs (also referred to as vaccination programs) were established, smallpox has been eradicated, poliomyelitis has been eliminated in the United States, and the other diseases are now under control. Other infectious diseases (cholera, tuberculosis, and sexually transmitted diseases) also are under control, in part due to the efforts of public health agencies and programs.

Is public health the same as medicine? Despite the fact that medical and public health services both seek to improve health, they are not the same. Two easy-to-remember differences are (1) public health services are directed at populations, and medical services are focused on the individual; and (2) public health services are mostly concerned with the prevention of disease whereas medical services are concerned with the diagnosis and treatment of disease. Public health and medicine are different, but they have the same objective of improving health and eliminating disease.

Definition of Epidemiology

Epidemiology is a word with Greek origins: from the Greek prefix epi, meaning “on, upon, or befall”; the Greek root demos, meaning “the people”; and the Greek suffix logos,” meaning “the study of.” In other words, epidemiology studies that which befalls on people, which is disease. The word epidemiology was first used in the 1700s to describe the science and methods used to study epidemics. In the twentieth century, with the decline of infectious diseases, epidemiology expanded to study more than epidemics. This decline in infectious diseases can be attributed to improvements in nutrition, sanitation, and general living conditions that in part resulted from public health interventions. Of course, these public health interventions were established using information provided by epidemiology.

Given this new need for epidemiology, it has been defined as the study of the distribution and determinants of health-related states or events in specified populations and the application of this study to control health problems.¹ This means that epidemiology is used to identify the diseases in a population and to understand why these diseases exist. Another often-used definition is that epidemiology is the study of the distribution and determinants of health-related states and events in defined populations and the application of this study to the control of health problems.²

The Greek root of epidemiology and the two definitions have a common theme, namely, the people. The people are considered as a group, which is referred to as a population. This population-centered nature of epidemiology leads to one of the differences between public health services and medical services. Populations are groups of people who share some common characteristics. These characteristics are personal (age, sex, race, health behaviors), geographical (live in the same neighborhood, city, region, country, continent), and time. Populations may be large groups of people (population of the United States) or small groups (people in a neighborhood or in a factory).

Epidemiology is the study of factors affecting the health and illness of pop­ulations. It serves as the foundation of interventions made in the interest of public health and preventive medicine. It is considered a cornerstone method of public health research and is highly regarded in medicine for identifying risk factors for disease and determining the best treatment approaches to clinical practice. Epidemiology is considered by many to be a critical branch of public health. In fact, it is often referred to as the basic science of public health.

Epidemiology provides a framework of methods and principles from which information can be reviewed and analyzed in a way that public health problems can be identified and addressed. The epidemiological methods allow for disease definition as well as classification, identification, and planning for disease control measures. Epidemiology also provides the way to understand the relationship between the presence of factors that cause disease, called causal factors, and the development of disease (for example, smoking and heart disease).

Epidemiologists are the people who work every day using epidemiological principles and methods to make our lives better. Epidemiologists identify, measure, count, and control diseases, injuries, and causes of death. They also look for connections between disease and genetic, environmental, and behavioral factors. Once these connections are established, epidemiologists plan and develop interventions to prevent disease and promote health. This process of identifying connections and developing interventions is how epidemiology touches our lives in a positive way every day.

Let’s discuss some specific examples of how epidemiology has affected public health. In general terms, most of the significant improvements in the health of the people in the United States can be traced to accomplishments of public health.

An example of how public health policy improved the health and well-being of large groups of people happened in the United States in 1955. At that time, results of field tests of the polio vaccine were announced indicating that an inactivated poliovirus could produce immunity. Within days of this announcement, a national vaccination program was implemented. Today, polio has been eradicated from the United States.

Another accomplishment of public health initiatives with long-term beneficial effects is the identification of the relationship between cigarette smoking and lung cancer and heart disease. Public health and epidemiological reports were instrumental in alerting people to the hazards of cigarette smoking, which led to the warning on cigarette packages from the U.S. Surgeon General. Public health, using epidemiological information as support, has worked hard in the past few decades to decrease the number of smokers in the United States. Figure 1.1 shows the results of this effort.

FIGURE 1.1: Cigarette smoking in the United States, 1965 to 2005

Source: CDC/NCHS, Health, United States, 2009, Figure 6. Data from the National Health Interview Survey and the Youth Risk Behavior Survey.

Figure 1.1 shows that the percentage of people who smoke has drastically decreased since 1965. This reduction has been most significant in men. In 1965 more than 50 percent of men in the United States were smo...