Applied Epidemiology

Background and Historical Evolution

Epidemiology is often considered the key scientific underpinning of public health practice. The pivotal role of epidemiology was emphasized by the Institute of Medicine in its definition of the substance of public health as “organized community efforts aimed at the prevention of disease and promotion of health. It links many disciplines and rests upon the scientific core of epidemiology” (Committee for the Study of the Future of Public Health, 1988, p. 41).

Since 1927, dozens of definitions of epidemiology have been put forth. A widely accepted version is the study of the distribution and determinants of health-related states or events in specified populations, and the application of this study to control of health problems. Perhaps the most comprehensive definition, and the one most relevant to public health practice, and applied work was crafted by Terris (1992):

Epidemiology is the study of the health of human populations. Its functions are:

• To discover the agent, host, and environmental factors which affect health, in order to provide the scientific basis for the prevention of disease and injury and the promotion of health.
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• To determine the relative importance of causes of illness, disability, and death, in order to establish priorities for research and action.
• To identify those sections of the population which have the greatest risk from specific causes of ill health, in order that the indicated action may be directed appropriately.
• To evaluate the effectiveness of health programs and services in improving the health of the population. (p. 912)

Each of these four functions has a direct application toward improving the overall health of the population. Recognition of epidemiology's role in improving the overall health of the public was not consistently present in early definitions.

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