Introduction
Cohort studies have an intuitive logic to them, but they can be very problematic when one is investigating outcomes that only occur in a small fraction of exposed and unexposed individuals. They can also be problematic when it is expensive or very difficult to obtain exposure information from a cohort. In these situations a case-control design offers an alternative that is much more efficient. The goal of a case-control study is the same as that of cohort studies, i.e., to estimate the magnitude of association between an exposure and an outcome. However, case-control studies employ a different sampling strategy that gives them greater efficiency.
Learning Objectives
After completing this module, the student will be able to:
- Define and explain the distinguishing features of a case-control study
- Describe and identify the types of epidemiologic questions that can be addressed by case-control studies
- Define what is meant by the term "source population"
- Describe the purpose of controls in a case-control study
- Describe differences between hospital-based and population-based case-control studies
- Describe the principles of valid control selection
- Explain the importance of using specific diagnostic criteria and explicit case definitions in case-control studies
- Estimate and interpret the odds ratio from a case-control study
- Identify the potential strengths and limitations of case-control studies
