Chapter Outline
Introduction Philosophic Framework Focus and Uses of Epidemiology Current Issues in Health Care Administration The Concept of Populations and Communities Managing Health Care for Populations and Communities The Role of Epidemiology Summary Study Questions
Learning Objectives
Upon completing this chapter, the reader will be able to do all of the following:
Define epidemiology
Discuss the history of epidemiology
Define managerial epidemiology
Discuss the distinction between observational and experimental epidemiology
Describe the uses of epidemiology
Describe the field of social epidemiology
Discuss the concept of populations and population health care management
Introduction
Epidemiology is recognized as a core discipline within the field of public health. It is a unique discipline that formally began as a result of the sanitary reform movement in seventeenth- and eighteenth-century England. Epidemiology is formally defined in a number of ways. First, epidemiology is the study of the distribution and determinants of diseases and injuries in human populations (Mausner and Kramer, 1985). A second definition emphasizes the study of all factors that affect the occurrence of health and disease in populations and their interdependence. Finally, 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 (Last, 1995).
Common to all of these definitions is the concept of populations. Individuals are not the focus of epidemiology; groups of individuals are. Populations may represent large groups, such as the total population of the United States, or small groups, such as the employees of a factory, store, or government agency. Central to the concept of populations is that groups of individuals exhibit certain commonalities. For example, a group of individuals who are related geographically, such as those living in the same city, represent a population. A group of individuals who work in the same setting are a population. And a group of individuals who live and work together are a population, as in the case of military personnel. Groups of individuals of the same race or ethnic group are also considered populations.
Historically, epidemiology is a discipline that has experienced long and distinct development stages. It is reasonable to think that epidemiology began when humans first walked on earth. Darwin's theory of the "survival of the fittest" can be extended to assume that early humans acquired, over time, an understanding of the relationship between environment and health. One simple example is the use of animal hides and furs as protective clothing.
The relationship between the environment and health and disease is mentioned in the Old Testament. However, it wasn't until the Greek civilization was established that epidemiology began to emerge as a scientific discipline. Hippocrates (460-377 B.C.) wrote the classic work "On Airs, Waters, and Places," the first known treatise on what is referred to today as environmental epidemiology. His writing discussed the link between the environment and human health. Hippocrates provided accurate descriptions of the diseases tetanus, typhus, and phthisis (Singer and Underwood, 1962). His contribution, which is also the first documented use of observational techniques, earned Hippocrates the title of "father of epidemiology" and the designation as the first epidemiologist (Newcomb and Marshall, 1990).
In the 1600s, John Graunt developed the demographic approach to health and disease investigations. Graunt used quantitative methods to study sex differences in deaths and diseases, geographic differences in death rates (rates were found to be higher in cities), and age differences in death rates (infant mortality rates were high). His work represents a significant advancement in epidemiology from an observational to a quantitative discipline, and Graunt is considered the founder of the discipline known as demography (Dupaquier and Dupaquier, 1985). His work is referred to as the starting point of modern epidemiology (Newcomb and Marshall, 1990).
Another seventeenth-century epidemiologist was Thomas Sydenham, who is called the English Hippocrates (Meynell, 1988). Sydenham reemphasized and expanded the theories of Hippocrates. He was the first to describe the clinical manifestations of the condition known as Bell's palsy. He reinitiated scientific observations of health, Hippocrates' contribution, into the core fabric of modern epidemiology.
Medical registration of deaths began in Great Britain in 1801. William Farr (1807-1883), a statistical abstracter in the General Registry Office in London, established a national system of recording causes of death (Eyler, 1980). This standard classification system was the precursor to the International Classification of Diseases and Related Conditions (ICD). Farr's other contributions included involvement in the first modern census, use of the census to collect specific information on diseases and conditions (blindness and deafness), and invention of the standardized mortality rate (Newcomb and Marshall, 1990).
A colleague of William Farr, John Snow, used epidemiologic principles to study outbreaks of cholera in London in the 1850s (Lilienfeld, 2000). Snow demonstrated how scientific evidence can be used to support hypotheses and analytic investigations. He identified the source of the infectious agent, contaminated water, and the etiology of the cholera outbreak (Collins, 2003). His work has been described as a brilliant use of descriptive and quantitative epidemiologic principles (Winkelstein, 1995).
The years leading up to World War II marked the beginning of another important period in the development of epidemiology as a scientific discipline. Epidemiologic methods continued to evolve, with a focus on individual diseases and conditions. The case-control study design was developed during the 1930s. Cohort studies were pursued to observe the relationship of tobacco use and disease. Case-control studies became very popular in hospital-based studies, beginning around 1950 (Levin and others, 1950; Wynder and Graham, 1950; Doll and Hill, 1950). Since then, epidemiology has continued to develop as cohort studies and clinical trials have gained popularity. Well-known cohort studies include the Framingham Heart Study (Gordon and others, 1977) and the Bogalusa Heart Study (Voors and others, 1976).
At the dawn of the twenty-first century, epidemiology has begun to expand its focus to health status, health-related quality of life, and burden of disease. As a result of the terrorist attacks on the United States on September 11, 2001, epidemiology has taken on new roles in bioterrorism preparedness and management of health care services. With the significant number of emerging infectious diseases (including AIDS and SARS), epidemiology's initial role in the study of epidemics will regain prominence.
Philosophic Framework
Our population-based perspective on epidemiology lends itself quite well to the objectives of health care management in the twenty-first century. These new objectives- focused on populations, not individual patient care-have forced a modification in the focal point of the science of epidemiology, which calls for the specialized concentration known as managerial epidemiology. Managerial epidemiology is one result of the contemporary demands of epidemiology and has become the core discipline for planning and managing health care for populations. A functional definition of managerial epidemiology-the use of epidemiology for designing and managing the health care of populations-is the study of the distribution and determinants of health and disease, including injuries and accidents, in specified populations and the application of this study to the promotion of health, prevention, and control of disease, the design of health care services to meet population needs, and the elaboration of health policy.
This adaptation of epidemiology to a managerial focus has been nurtured by many different external forces. One set of forces is the transition from a traditional role of the health care executive to a population orientation. The traditional role of the health care executive has been in a facility context, encompassing such general management functions as planning, organization, leadership, and control. These functions all emphasize the management of facilities and personnel that provide health care services. Planning involves many activities, but in general, it is the determination of courses of action for individuals and organizations. Organization is essential for the coordination of activities and resources, both human and physical. Leadership is centered on the ability or skill to motivate and manage people. Control involves monitoring and periodically evaluating these activities.
The discipline of health care management continues to evolve from the individual patient perspective toward a managed population perspective. The current stage of evolution is highlighted by management of a network of services, management across traditional organizational boundaries, and management of the continuous improvement of quality of care (Shortell and Kaluzny, 1997).
The primary evolutionary pressures on the discipline of managerial epidemiology are cost containment and an underlying desire to maintain and improve the quality of health care. Epidemiology has emerged as a primary discipline in achievement of the population-oriented objectives of health care management.
Focus and Uses of Epidemiology
Epidemiology initially centered on observations and descriptions of health and disease and factors associated with health and disease. During its maturation into a science, experimental considerations were added to the discipline in the twentieth century. Over time, epidemiology developed a specificity for individual diseases, etiologic constellations (injury, chronic disease, and infectious disease epidemiology, for example), and situational uses (including environmental, occupational, molecular, and managerial epidemiology). Both observational and experimental aspects are characteristic in all of the uses of epidemiology.
Observational Epidemiology
Observational epidemiology involves the observation of health and disease in a population and the analysis of these observations. Observational study activities are the most common in epidemiology. Observational study methods include descriptive studies, historically the first type of epidemiologic study, and analytic epidemiologic study designs (cross-sectional, cohort, and case-control designs). Cross-sectional studies measure the prevalence of health and disease in a population. Cohort and case-control studies measure the incidence and risk of health and disease in a population. Chapter Four presents a thorough discussion of these concepts.
Experimental Epidemiology
Experimental epidemiology is concerned with planned studies in which the exposure to potential health and disease risk factors is controlled. The objective of this method is to improve the validity, or accuracy, of epidemiologic studies. Exposure to potential risk factors is accomplished by random assignment. This randomization is used to avoid bias in the study and to ensure validity. Clinical trials are the most commonly used experimental study design. Chapter Four discusses experimental epidemiology in greater detail.
Preventive Medicine
Epidemiology and medicine have always been linked as scientific disciplines. Epidemiology is an important tool of community health and preventive medicine. Specific uses of epidemiology have included determining etiologic or causal factors of diseases; describing factors that are associated with adverse conditions; community diagnosis of the distribution of disease; predicting disease occurrence, impact, and distribution; estimating the individual risk of suffering from diseases; evaluating preventive therapeutic and intervention activities; measuring the efficacy of health measures; studying historical disease trends; identifying disease syndromes; planning for current health needs; and predicting future needs.
Epidemiology plays a major role in controlling the distribution, frequency, and severity of disease in populations. This is accomplished through prevention of new cases (known as primary prevention), as well as by eliminating existing disease profiles and improving the health status and survival of individuals with those diseases (known as secondary and tertiary prevention). Primary prevention involves the removal or modification of intrinsic and extrinsic factors that effect a change in health status from absence of disease to preclinical disease. Primary preventive measures include health promotion and specific preventive measures. Health promotion involves health education and the provision of conditions that influence health (adequate food, housing, clothing, and so on). Specific preventive measures target diseases and groups of individuals, often based on the risk of acquiring a disease. These measures include purification of water supplies, immunization, protection from occupational hazards (for example, proper clothing and protective equipment), and protection from accidents (seat belts, for example).
Secondary prevention, which involves screening, early disease detection, and early treatment, often allows for the reversal or delay of the progression from preclinical to clinical disease. This is particularly beneficial in diseases for which control measures exist, such as hypertension. Tertiary prevention involves arresting the progression from clinical disease to disability and reversal of progression from disability to death, with restoration of function through rehabilitation.
Current Issues in Health Care Administration
The health policy experiments of various states, and the periodic policy debates at the federal level, focus on the evaluation and reformation of the manner in which health is promoted and disease and associated disability are controlled in the United States. The notions of improved or even universal access to more comprehensive and cost-effective health care services and the reduction of unnecessary or unproven services are central to such health system reform discussions. Understanding the health status and needs of populations is essential to the proper planning and organization of the health care system.
Contemporary reform of the U.S. health care delivery system from a federal standpoint began in 1965, when Title XVIII of the Social Security Act Amendments created Medicare and Title XIX created Medicaid. Medicare provided financing of health care services for citizens over the age of 65 and for the disabled. Medicaid provided financing of health care services for the medically indigent. These programs were driven by the concept of social equity and represent the first time that the federal government became involved with the financing and delivery of health care services for the general population.
In 1973, Congress passed the Health Maintenance Organization Act, which encouraged the formation and proliferation of health maintenance organizations (HMOs). The intent of this legislation was cost containment. The federal government began to recognize that the HMO model, when successful, reduces the cost of providing health care services and can motivate secondary and even primary prevention activities. This reform movement emphasized the federal government's concern with the cost of health care. A major change in the Medicare program occurred in 1982 with the creation of the prospective payment system (PPS). PPS was created by an act of Congress and focused on in-hospital Medicare charges (often known as "Part A"). A result of PPS was the establishment of diagnosis-related groups (DRGs) to permit the comparison of like admissions and the regulation of their cost. In 1990, Medicare was further reformed with the establishment of the resource-based relative value scale (RBRVS) for reimbursement of physician services (often known as "Part B"). RBRVS is an extension of PPS, and its intent is also cost containment. In 2000, additional PPS efforts were implemented by Medicare's mandate to use the ambulatory patient classification (APC). Payment for services under the outpatient PPS system is based on combining outpatient services into APC groups.
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