cohort study

Syllable breakdown

Dictionary meaning

an observational study design in which a defined group of people — the cohort — who share a common characteristic such as birth year, occupation, or exposure status, is followed over time and the rates of health outcomes are compared between those with and without a specific exposure; prospective cohort studies follow participants forward from the present into the future, collecting exposure data before outcomes occur; retrospective cohort studies identify past exposure from historical records and then ascertain subsequent outcomes; cohort studies are better suited than case-control studies to estimating absolute risk and incidence rates, can study multiple outcomes of a single exposure, and avoid the recall bias that affects retrospective case-control designs; their limitations include cost and time for prospective designs, loss to follow-up, and confounding by measured and unmeasured factors; classic cohort studies include the Framingham Heart Study and the British Doctors' Study on smoking and lung cancer

Examples

• The occupational cohort study followed 10,000 factory workers for 25 years and found a fourfold elevation in mesothelioma risk among those exposed to asbestos.
• The Nurses' Health Study, a prospective cohort study begun in 1976, has generated hundreds of publications on women's health outcomes.

Synonyms: longitudinal study, follow-up study, prospective study