Nested case control study

Nested case control study (pronunciation: nes-ted kās kən-ˈtrōl ˈstə-dē) is a type of observational study in epidemiology that is derived from a cohort study. The procedure involves selecting subsets of controls from the population group that gives rise to the cases. This is done in such a way that each control is selected knowing that the case for which it is a control has occurred.

Etymology

The term "nested" refers to the fact that the case-control study is carried out within the confines of a cohort study. The term "case control" refers to the method of identifying cases (those with the outcome of interest) and controls (those without the outcome of interest) and comparing the exposure history between the two groups.

Procedure

In a nested case control study, cases of a disease that occur in a defined cohort are identified and, for each, a specified number of matched controls is selected from among those in the cohort who have not developed the disease by the time of disease occurrence in the case. For many research questions, the nested case control design potentially offers impressive reductions in costs and efforts of data collection and analysis compared with the full cohort approach, with relatively minor loss in statistical efficiency.

Advantages

The main advantage of a nested case control study is that it can provide similar information to a cohort study, but with a significantly reduced amount of time and cost. This is because it is not necessary to follow up with the entire cohort over time. Instead, only a subset of the cohort, the cases and their matched controls, need to be followed up.

Disadvantages

One of the main disadvantages of a nested case control study is that it can be less statistically powerful than a full cohort study because it uses a subset of the cohort rather than the full cohort. This means that it may not detect associations that a full cohort study might detect.

Related Terms

• Observational study
• Cohort study
• Case control study
• Epidemiology

External links

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

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