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| case–control study | |
|---|---|
| Name | Case–control study |
| Type | Observational study |
| Purpose | Investigate associations between exposures and outcomes |
case–control study A case–control study is an observational research design that compares individuals with a specific outcome (cases) to individuals without that outcome (controls) to identify prior exposures or risk factors. Originating in early epidemiologic research, the design has been applied across public health, clinical medicine, and social inquiry to investigate infectious diseases, chronic conditions, occupational risks, and rare events.
Case–control studies emerged alongside landmark investigations such as those surrounding John Snow, the Broad Street cholera outbreak, and later public health responses involving institutions like the Centers for Disease Control and Prevention and the World Health Organization. Influential figures including William Farr, Richard Doll, Austin Bradford Hill, Thomas McKeown, and Sir Austin Bradford Hill contributed to methods still in use. Major events shaping methodology include the 1950s smoking and lung cancer research, debates at the Royal Society of Medicine, and methodological syntheses from organizations like the National Institutes of Health and the Royal Society.
Design principles were refined in contexts such as the Framingham Heart Study, the British Doctors Study, and analyses performed by teams at the Mayo Clinic, the Johns Hopkins Hospital, and the London School of Hygiene & Tropical Medicine. Methodological tools draw on statistical foundations developed by mathematicians and statisticians affiliated with University of Oxford, Harvard University, University of Cambridge, Columbia University, and Princeton University. The design contrasts with cohort studies evident in research at the Nurse's Health Study and randomized trials such as those at the Medical Research Council and the Food and Drug Administration.
Case definitions often mirror diagnostic criteria from bodies like the American Medical Association, the World Health Organization, and disease registries such as the Surveillance, Epidemiology, and End Results Program. Case ascertainment can utilize data from hospitals such as Massachusetts General Hospital and registries run by institutions like the Cancer Research UK or systems like the Veterans Health Administration. Control selection strategies have been debated in forums at Stanford University, Yale University, University of California, Berkeley, and during conferences at the Rockefeller Foundation and the Kaiser Permanente research divisions.
Analysis typically uses measures such as the odds ratio, logistic regression, and conditional logistic models implemented by software developed by firms and groups associated with SAS Institute, StataCorp, R Project, and academic centers at Imperial College London and Duke University. Statistical inference methods have been advanced by scholars linked to Princeton University, University of Chicago, University of Pennsylvania, and the London School of Economics. Classic analytic examples include studies on smoking and lung cancer published in journals associated with The Lancet, The New England Journal of Medicine, and BMJ.
Discussions of bias and confounding reference historical critiques and methodological advances emerging from workshops at the Royal Statistical Society, the American Statistical Association, and institutions like the Cochrane Collaboration. Investigations into recall bias, selection bias, and measurement error have involved researchers affiliated with Harvard School of Public Health, Yale School of Public Health, and the Johns Hopkins Bloomberg School of Public Health. Legal and ethical implications have been debated in contexts linked to commissions such as the National Commission for the Protection of Human Subjects of Biomedical and Behavioral Research and panels at the World Health Assembly.
Specialized forms include nested case–control studies within cohorts from projects like the Framingham Heart Study and case–cohort designs used in consortia such as the International Agency for Research on Cancer collaborations. Extensions and hybrid designs have been applied in settings involving biobanks from institutions like the UK Biobank, multi-center networks such as the Global Burden of Disease collaborators, and trials coordinated by organizations like the Wellcome Trust.
Applications span infectious disease outbreaks (investigations tied to HIV/AIDS emergence, SARS outbreaks, and Ebola virus epidemic responses), chronic disease research exemplified by studies on lung cancer, coronary artery disease, and Type 2 diabetes mellitus, occupational exposures examined in cases from Chernobyl aftermath studies, and pharmacovigilance work monitored by regulators such as the European Medicines Agency, the Food and Drug Administration, and the World Health Organization. Prominent case–control investigations have informed policy decisions in contexts involving commissions like the Royal Commission and advisory panels at the National Academies.