Prospective cohort study
A prospective cohort study is a cohort study that follows over time a group of similar individuals (cohorts) who differ with respect to certain factors under study, to determine how these factors affect rates of a certain outcome. For example, one might follow a cohort of middle-aged truck drivers who vary in terms of smoking habits, to test the hypothesis that the 20-year incidence rate of lung cancer will be highest among heavy smokers, followed by moderate smokers, and then nonsmokers.
The prospective study is important for research on the etiology of diseases and disorders in humans because for ethical reasons people cannot be deliberately exposed to suspected risk factors in controlled experiments.
One of the advantages of prospective cohort studies is they can help determine risk factors for being infected with a new disease because they are a longitudinal observation over time, and the collection of results is at regular time intervals, so recall error is minimized. 
- "Definition of prospective cohort study - NCI Dictionary of Cancer Terms".
- Manolio TA, Bailey-Wilson JE, Collins FS (October 2006). "Genes, environment and the value of prospective cohort studies". Nat. Rev. Genet. 7 (10): 812–20. doi:10.1038/nrg1919. PMID 16983377.
- Porta M (editor). A dictionary of epidemiology. 5th. edition. New York: Oxford University Press, 2008. Edited by Miquel Porta 
This article incorporates public domain material from the U.S. National Cancer Institute document "Dictionary of Cancer Terms".Template:Hoang Trong Sang Medical research studies
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