30 lines
2.7 KiB
Markdown
30 lines
2.7 KiB
Markdown
---
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title: "Case–control study"
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chunk: 2/2
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source: "https://en.wikipedia.org/wiki/Case–control_study"
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category: "reference"
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tags: "science, encyclopedia"
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date_saved: "2026-05-05T09:49:25.991019+00:00"
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instance: "kb-cron"
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---
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== Examples ==
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One of the most significant triumphs of the case–control study was the demonstration of the link between tobacco smoking and lung cancer, by Richard Doll and Bradford Hill. They showed a statistically significant association in a large case–control study. Opponents argued for many years that this type of study cannot prove causation, but the eventual results of cohort studies confirmed the causal link which the case–control studies suggested, and it is now accepted that tobacco smoking is the cause of about 87% of all lung cancer mortality in the US.
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== Analysis ==
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Case–control studies were initially analyzed by testing whether or not there were significant differences between the proportion of exposed subjects among cases and controls. Subsequently, Cornfield pointed out that, when the disease outcome of interest is rare, the odds ratio of exposure can be used to estimate the relative risk (see rare disease assumption). The validity of the odds ratio depends highly on the nature of the disease studied, on the sampling methodology and on the type of follow-up. Although in classical case–control studies, it remains true that the odds ratio can only approximate the relative risk in the case of rare diseases, there is a number of other types of studies (case–cohort, nested case–control, cohort studies) in which it was later shown that the odds ratio of exposure can be used to estimate the relative risk or the incidence rate ratio of exposure without the need for the rare disease assumption.
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When the logistic regression model is used to model the case–control data and the odds ratio is of interest, both the prospective and retrospective likelihood methods will lead to identical maximum likelihood estimations for covariate, except for the intercept. The usual methods of estimating more interpretable parameters than odds ratios—such as risk ratios, levels, and differences—is biased if applied to case–control data, but special statistical procedures provide easy to use consistent estimators.
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== See also ==
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Nested case–control study
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Retrospective cohort study
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Prospective cohort study
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Randomized controlled trial
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== References ==
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== Further reading ==
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Stolley, Paul D., Schlesselman, James J. (1982). Case–control studies: design, conduct, analysis. Oxford [Oxfordshire]: Oxford University Press. ISBN 0-19-502933-X. (Still a very useful book, and a great place to start, but now a bit out of date.)
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== External links ==
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Wellcome Trust Case Control Consortium |