Epidemiology for nutritionists: 3. The design of studies
1983
Burr, Michael L.
The design criteria for nutritional epidemiological studies are identified and discussed for each of 4 types of studies: cross-sectional, retrospective, prospective, and intervention. A cross-sectional survey examines a population group at a specific point in time, and is perhaps the most straightforward, rapid type of epidemiological study. A typical survey of this type is undertaken to ascertain a population characteristic (e.g., protein intake) in order to detect untreated cases of a disorder, construct comparisons between different groups of people, and to investigate associations between 2 or more variables, often to test an etiological hypothesis. Retrospective studies attempt to associate causes with effects, by collecting information about past events, and are typified by the case-control design, which has been used in every branch of medical and clinical practice. Prospective studies look forward from causes to effects in cohort populations. Intervention studies employ the sensitive design of randomized controlled trials to assess 1 factor while keeping others constant. Examples of applications of these 4 types of epidemiological studies in nutritional assessment are provided. (wz)
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