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What is a case-control study?

A case-control study is a type of observational research study that compares two different groups which have a defined different outcome and an attempt to identify a cause and effect relationship between the outcome and some factor. 

What are the benefits of a case-control study?

One benefit of case-control studies is that they are useful in the study of rare diseases, as well as diseases that may have a long onset period after the exposure. Case-control studies also allow for the examination of numerous risk factors at once. This is useful when disease outbreaks occur, since researchers are able to examine potential exposures leading to the disease. 

How is a case-control study conducted?

To conduct a case-control study, the cases must be identified as those with the outcome being studied and the controls are identified as those without the outcome within a defined population. Data is gathered from both groups regarding exposures being evaluated. Data is then analyzed regarding exposures between cases and controls to determine potential correlations between exposure and outcome. 

What are the limitations of a case-control study?

One limitation of case-control studies is recall bias. Since the participants are being examined regarding past exposures, they may not recall information accurately. This bias tends toward the case group having better recall to exposures, even if both the cases and the controls had the same exposures. Another limitation is the inability to determine causation in this type of study, but only correlations. 

What is the difference between a case-control study and a cohort study?

Although these two studies are often mistaken for one another, a case-control study is different from a cohort study. Case-control studies begin by identifying a group that has developed a disease or outcome and a group that has not developed this outcome. Data on past exposures are then compared between these groups. A cohort study, specifically a retrospective cohort study, uses pre-existing data to look back in time to identify potential exposures that may have led to a disease or outcome within a cohort. 

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Photo of Kristin Ricklefs-Johnson

Medically reviewed by:

Kristin Ricklefs-Johnson, Ph.D., RD

Kristin is an RDN who also earned her Ph.D. in Nutrition from Arizona State University with an emphasis on insulin resistance, lipid metabolism disorders, and obesity. She completed her post-doctoral fellowship at Mayo Clinic where she focused on nutrition-related proteomic and metabolic research. Her interests include understanding the exact mechanism of action of various genetic variations underlying individual predispositions to nutrition-related health outcomes. Her goal is to help all individuals prevent chronic diseases and achieve long, healthy lives through eating well.

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