Epidemiologic study designs Epidemiology （流行病学研究设计流行病学）.pdfVIP

8. Analytic study designs The architecture of the various strategies for testing hypotheses through epidemiologic studies, a comparison of their relative strengths and weaknesses, and an in-depth investigation of major designs. Epidemiologic study designs In previous topics we investigated issues in defining disease and other health-related outcomes, in quantitating disease occurrence in populations, in relating disease rates to factors of interest, and in exploring and monitoring disease rates and relationships in populations. We have referred to cohort studies, cross-sectional, and case-control studies as the sources of the measures we examined, but the study designs themselves were secondary to our interest. In the present chapter we will define and compare various study designs and their usefulness for investigating relationships between an outcome and an exposure or study factor. We will then examine two designs – intervention trials and case-control studies – in greater depth. The study designs discussed in this chapter are called analytic because they are generally (not always) employed to test one or more specific hypotheses, typically whether an exposure is a risk factor for a disease or an intervention is effective in preventing or curing disease (or any other occurrence or condition of interest). Of course, data obtained in an analytic study can also be explored in a descriptive mode, and data obtained in a descriptive study can be analyzed to test hypotheses. Thus, the distinction between descriptive and analytic studies is one of intent, objective, and approach, rather than one of design. Moreover, the usefulness of the distinction is being eroded by a broad consensus (dogma?) in favor of testing hypothe