What Is a Case Control Study?

A case control study is intended to research a subject and understand whether a result is a consequence of a certain exposure, for example, if working conditions cause some sickness in workers. Plainly put, the connection between the cause and the effect define case control study.

Such a task is common in medical and psychological researches. No wonder that students of medicine and psychology often face it. Still, this type of report is also used in other sciences.

Basically, what you need to do when you are assigned a case control study is to define the cases and the controls and to compare them, analyzing which group had the exposure and how this affected them. The cases are a group of people who had the outcome you are investigating, while the controls are those who are known to have no outcome.

Such investigations are different from other types of papers you had to write. The thing is you are analyzing the outcomes you already know instead of analyzing information for the purpose of finding those outcomes. This means the research is retrospective. To some students, a hard part is to understand this and not confuse the purpose of investigation.

Advantages and Disadvantages of Case Control Studies

There are always certain advantages and disadvantages in all study methods. Case control studies have proved to be relatively inexpensive, quick, and easy to perform, which obviously is a benefit. The best use of this type of study is to research rare outcomes and investigate outbreaks.

The possibility of receiving quick results is probably the best advantage because it allows the investigator to conduct a preliminary research of a risk factor. The findings often appear to be a solid reason to start a more substantial and expensive investigation in the future. Another advantage is the ability to investigate and analyze a few exposures at once.

However, there is a significant drawback of case control studies – the proneness to rising bias. The reason for bias is the retrospective nature of the investigation. Most of the data will be based on people’s memory, and the group of people who had the outcome will likely be more motivated to recollect the risk factors than the group of those who had not will be. Some other disadvantages are the impossibility to study several outcomes at a time, the inability to evaluate incidence rates (if you are researching a disease), the difficulty of identifying the influence of time passed between the exposure and the outcome.

Case Control Study Design

Case Control Study

When you are ready to start working on a case study, pay attention to the following important issues:

  • Clear and comprehensible hypothesis.
    Any paper begins with introducing a key idea, a purpose of a research, a thesis statement, etc. With this type of paper, you will need to formulate a hypothesis at the initial stage.
  • Case definition.
    It’s important that all people with the outcome are selected basing on a single criterion and defined clearly in the introductory part. You also need to define how you have found them.
  • Incident and prevalent cases.
    An incident case is a group of people who have been newly diagnosed within some time period. This selection is recommended since it is easier for people to recall the exposures under research. Besides, it’s easier to identify the time relations between the exposure and the result.
    A prevalent case is a group of people who have been under investigation for a definite period of time when the outcome had been noticed. This selection is less recommended because such people may fail to give an accurate evaluation of the exposures. It’s quite difficult here to understand whether the exposure happened before the outcome developed or the exposure was one its results.
  • Sources of cases.
    You can find the objects of your research in clinics and hospitals as well as among the common people. The latter usually requires more resources in terms of money and effort.
  • Selection of controls.
    To put it plainly, a perfect group of controls would be randomly selected common people who had the same exposure (the same amounts and the same frequency) but no outcome. The source of them should also be the same as the source of cases, i.e. the same population living in the same area of the same age and sex.
    It’s important for the both groups to be similar but don’t overdo here, or else you are risking to have an insufficient number of controls.

Final Tips

The key to performing a successful case control study is doing everything in a similar way. Both groups should be very similar, and you need to study them similarly. That is, apply the same methods and tools to both groups.

It’s important to be very objective. Remember that the research is retrospective, so you are working with the outcome that is already known. You may face the problem of trying to subconsciously match the exposure with the outcome even if they don’t relate to each other. Considering this, working on a case control study in groups is ideal because you can divide the tasks and make sure the person who collects data about the risk factor and talks with people participating in the investigation doesn’t know what the outcome is. Thus, you will eliminate the risk of researcher bias.

Also, since the controls will be less accurate with remembering their past, it’s a good idea to help them by educating them on potential risk factors they could ignore or fail to notice.

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