Nested case–control study

Nested case–control study (pronunciation: nes-ted kās-kən-ˈtrōl stə-dē) is a type of observational study in epidemiology that is derived from a cohort study. The procedure of a nested case–control study is as follows: from an assembled population in a cohort study, cases of a disease that occur are identified and, for each, a specified number of matched controls is selected from those in the cohort who have not developed the disease by the time of disease occurrence in the case.

Etymology

The term "nested" refers to the fact that the case–control study is embedded (nested) within a larger cohort study. The term "case–control" refers to the method of identifying and comparing cases and controls.

Procedure

In a nested case–control study, the exposure status is measured only among the cases and the selected controls. This approach can save time and cost, especially when exposure data is expensive or difficult to obtain. The nested case–control study is particularly advantageous when exposure assessment is expensive or difficult.

Advantages and Disadvantages

The main advantage of a nested case–control study over a full cohort analysis is efficiency. As the outcome of interest has already occurred, it is possible to only measure exposures in those who have developed the disease (cases) and a small subset of those who have not (controls). This can result in substantial cost and time savings.

However, a potential disadvantage is that the selection of controls can introduce bias. This can occur if controls are not representative of the cohort as a whole, or if the selection of controls is related to the exposure.

Related Terms

• Cohort study
• Case-control study
• Observational study
• Epidemiology
• Disease
• Population

External links

• Medical encyclopedia article on Nested case–control study
• Wikipedia's article - Nested case–control study

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