SeriesDescriptive studies: what they can and cannot do
Section snippets
Five “W” questions
Traditional descriptive epidemiology has focused on three key features: person, place, and time,4 or agent, host, and environment.5 An alternative approach is that of newspaper coverage. Good descriptive research, like good newspaper reporting, should answer five basic “W” questions—who, what, why, when, and where—and an implicit sixth question, so what?
Who has the disease in question? Age and sex are universally described, but other characteristics might be important too, including race,
Types of descriptive studies
Descriptive studies consist of two major groups: those that deal with individuals and those that relate to populations. Studies that involve individuals are the case report, the case-series report, cross-sectional studies, and surveillance, whereas ecological correlational studies examine populations.4
Trend analysis
Descriptive studies have several useful roles. Being able to monitor the health of populations is important to health-care administrators. Trend analysis is often provided by ongoing surveillance. Examples include the emerging epidemic of syphilis in the Russian Federation,52, 53 and the international epidemic of multiple births, prematurity, and low birthweight caused by assisted reproductive technologies.54, 55, 56, 57, 58 Both epidemics raise troubling societal issues.
Planning
A second use is
Advantages and disadvantages
Descriptive studies have both strengths and weaknesses. Often, the data are already available and thus inexpensive and efficient to use. Furthermore, few ethical difficulties exist. However, descriptive studies have important limitations. Temporal associations between putative causes and effects might be unclear. A dangerous pitfall is that the investigators might draw causal inferences when none is possible.27
Conclusion
Descriptive studies are often the first, tentative approach to a new event or condition. These studies generally emphasise features of a new disease or assess the health status of communities. Health administrators use descriptive studies to monitor trends and plan for resources. By contrast, epidemiologists and clinicians generally use descriptive reports to search for clues of cause of disease—ie, generation of hypotheses. In this role, descriptive studies are often a springboard into more
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