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	Retrospektiv kohortstudie	Kohortstudie
Ämnesområde	Epidemiologi	Epidemiologi
Familj	Process / pipeline	Process / pipeline
Ursprungsår	Mid-20th century (widely formalized 1950s–1970s)	Mid-20th century (formal epidemiological design codified ~1950s)
Upphovsperson	Systematic use attributed to early 20th-century occupational epidemiology; formalized in modern epidemiological theory by Brian MacMahon and others	Doll & Hill (British Doctors Study, 1951); Snow (cholera, 1854)
Typ	Observational analytic study	Observational longitudinal study design
Ursprungskälla	Rothman, K. J., Greenland, S., & Lash, T. L. (2008). Modern Epidemiology (3rd ed.). Lippincott Williams & Wilkins. ISBN: 978-0781755641	Rothman, K. J., Greenland, S., & Lash, T. L. (2008). Modern Epidemiology (3rd ed.). Lippincott Williams & Wilkins. ISBN: 978-0781755641
Alias	historical cohort study, non-concurrent cohort study, retrospective follow-up study, historical prospective study	longitudinal study, follow-up study, panel study, incidence study
Närliggande	6	6
Sammanfattning	A retrospective cohort study assembles a group of individuals who share a common starting point and reconstructs their exposure history and subsequent outcomes entirely from pre-existing records. Because the data have already been collected before the study begins, the design is far faster and cheaper than a prospective cohort; however, the researcher must work with whatever information was recorded at the time rather than collecting purpose-built measurements.	A cohort study assembles a group of individuals who share a common starting point — typically freedom from the outcome of interest — and follows them over time to observe who develops the outcome. By comparing incidence rates between exposed and unexposed subgroups, researchers can estimate relative risk and absolute risk differences. Cohort studies are the gold-standard observational design for measuring disease incidence and establishing temporal relationships between exposure and outcome.