CISN - How Cancer is Studied - Types of Epidemiology Studies

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Types of Epidemiology Studies - page 3

2. Case Control Studies: "Why me" study.

In case control studies investigators begin with people who have been diagnosed as having a disease (cases) and compare them to people without the disease (controls).

Using data from a variety of sources - personal interviews, medical and hospital records - cases and controls are compared with regard to past exposures in an attempt to identify differentiating factors.

Similarities with historical cohort studies
Both types of studies take a look backward in time for exposures that may be
related to disease.

Differences with historical cohort studies
Sample size


	In case-control studies, a relatively small group of cases is identified, and compared to an equal-sized group of matched controls. In historical cohort studies, a large cohort is divided among those who do versus do not have the disease.

Advantages of case controlled studies:

With enough subjects in the study and careful selection of controls, case-control studies provide a cost-effective way to study cancer.

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Disadvantages:

As in eyewitness testimony in a courtroom, case-control studies depend on our often unreliable memories.


		In case-control studies, cases and/or controls may remember their past diets differently. This is called 'recall bias'. Honesty in reporting is also an issue.

Image courtesy of American Institute of Cancer Research

New scientific developments may help avoid this problem. Biomarkers of dietary intake, which act like fingerprints of the foods we eat regularly, can be utilized vs. relying on faulty memories.

Summary of Analytical Study Designs

Most epidemiological studies are described as "hypothesis generating." That is, they identify trends in the general population that then confirm them in carefully controlled experimental settings.

The choice among the three types of epidemiological studies always reflects a trade-off among the goals (e.g., explore a single disease or multiple diseases) and the constraints (e.g., time and costs).

This chart shows strengths and weaknesses of several types of studies.

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