JENNIFER L. KELSEY DIANA B. PETITTI ABBY C. KING
As described in Chapter 1, epidemiology is used for many purposes. One is to determine the magnitude and impact of diseases or other conditions in populations or in certain segments of populations. This information can help to set priorities for investigation and control, to decide which subgroups of the population should be the focus of investigation, and to determine what types of treatment facilities are needed. Epidemiologic studies can also be used to ascertain the natural history, clinical course, and pathogenesis of disease. They can be used to evaluate disease prevention programs and preventive and therapeutic interventions. Most often, epidemiology is used to learn about the etiology of disease.
This chapter addresses methodologic concepts and issues that are most pertinent to epidemiology as it is used in public health settings and health care organizations. The intent is to give the reader an overview of key topics. The chapter assumes knowledge of the basics of epidemiology—the calculation of incidence and prevalence and the estimation of measures of association (relative risk and odds ratios). It does not cover statistical analysis of epidemiologic data or the mechanics of estimating sample size and statistical power. Instead it focuses on these concepts as they affect the design and interpretation of epidemiologic studies. Some of the material is adapted from other sources (Friedman 1994; Kelsey et al. 1996; Kelsey and Sowers 1996; Kelsey and Parker 1993), to which the reader is referred for more detail.
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