For other uses of "prospective", see Prospective (disambiguation).
A prospective cohort study is a longitudinalcohort 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. The distinguishing feature of a prospective cohort study is that at the time that the investigators begin enrolling subjects and collecting baseline exposure information, none of the subjects have developed any of the outcomes of interest. After baseline information is collected, subjects in a prospective cohort study are then followed "longitudinally," i.e. over a period of time, usually for years, to determine if and when they become diseased and whether their exposure status changes outcomes. In this way, investigators can eventually use the data to answer many questions about the associations between "risk factors" and disease outcomes. For example, one could identify smokers and non-smokers at baseline and compare their subsequent incidence of developing heart disease. Alternatively, one could group subjects based on their body mass index (BMI) and compare their risk of developing heart disease or cancer. Prospective cohort studies are typically ranked higher in the hierarchy of evidence than retrospective cohort studies and can be more expensive than a case–control study.
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.
The Strengthening the Reporting of OBservational studies in Epidemiology (STROBE) recommends that authors refrain from calling a study ‘prospective’ or ‘retrospective’ due to these terms having contradictory and overlapping definitions. STROBE also recommends that whenever authors use these words, they specify which definition they use, including a detailed description of how and when data collection took place.
This article incorporates public domain material from the U.S. National Cancer Institute document "Dictionary of Cancer Terms".
- ^"Definition of prospective cohort study - NCI Dictionary of Cancer Terms".
- ^LaMorte, Wayne. "Prospective and Retrospective Cohort Studies". Boston University College of Public Health. Retrieved Nov 25, 2013.
- ^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
- ^Vandenbroucke, Jan P; von Elm, Erik; Altman, Douglas G; Gøtzsche, Peter C; Mulrow, Cynthia D; Pocock, Stuart J; Poole, Charles; Schlesselman, James J; Egger, Matthias (2007-10-01). "Strengthening the Reporting of Observational Studies in Epidemiology (STROBE): Explanation and Elaboration". PLoS Medicine. 4 (10). doi:10.1371/journal.pmed.0040297. ISSN 1549-1277. PMC 2020496. PMID 17941715.
a careful examination of a phenomenon; see also design.
cohort studyprospective study.
cross-sectional study one employing a single point of data collection for each participant or system being studied. It is used for examining phenomena expected to remain static through the period of interest. It contrasts with a longitudinal s.
electrophysiological s's (EPS) studies from within the heart of its electrical activation and response to electrical stimuli and certain drugs. In general they include intravenous and/or intra-arterial placement of one or more electrode catheters at sites in the atria, ventricles, or coronary sinus, and sometimes the pulmonary artery or aorta. They record activity or stimulate the heart at various rates and cadences and are aids in the evaluation of electrophysiologic properties such as automaticity, conduction, and refractoriness. They also initiate and terminate tachycardias, map the sequence of activation, and aid in evaluation of patients for various forms of therapy and for the response to therapy. During these studies catheter ablation procedures, such as radio frequency ablation and electrical ablation, may be performed.
longitudinal study one in which participants, processes, or systems are studied over time, with data being collected at multiple intervals. The two main types are prospective studies and retrospective studies. It contrasts with a cross-sectional s.
pilot study a smaller version of a proposed research study, conducted to refine the methodology of the later one. It should be as similar to the proposed study as possible, using similar subjects, the same setting, and the same techniques of data collection and analysis.
prospective study an epidemiologic study in which the groups of individuals (cohorts) are selected on the bases of factors that are to be examined for possible effects on some outcome. For example, the effect of exposure to a specific risk factor on the eventual development of a particular disease can be studied. The cohorts are then followed over a period of time to determine the incidence rates of the outcomes being studied as they relate to the original factors in question. Called also cohort study.
The term prospective usually implies a cohort selected in the present and followed into the future, but this method can also be applied to existing longitudinal historical data, such as insurance or medical records. A cohort is identified and classified as to exposure to the risk factor at some date in the past and followed up to the present to determine incidence rates. This is called a historical prospective study, prospective study of past data, or retrospective cohort study.
retrospective study an epidemiologic study in which participating individuals are classified as either having some outcome (cases) or lacking it (controls); the outcome may be a specific disease, and the persons' histories are examined for specific factors that might be associated with that outcome. Cases and controls are often matched with respect to certain demographic or other variables but need not be. As compared to prospective studies, retrospective studies suffer from drawbacks: certain important statistics cannot be measured, and large biases may be introduced both in the selection of controls and in the recall of past exposure to risk factors. The advantage of the retrospective study is its small scale, usually short time for completion, and its applicability to rare diseases, which would require study of very large cohorts in prospective studies. See also prospective s.
urinary flow studyuroflowmetry.
voiding pressure study simultaneous measurement of bladder contraction, urinary flow, and sphincter electromyogram.
a scholarly examination. Specific types of study are also detailed under blind, case-control, cohort, cross-sectional.
one in which a phenomenon is described and an attempt made to analyze the effects of variables on the phenomenon.
one in which a phenomenon is described but no attempt is made to analyze the effects of variables on the phenomenon.
one carried out to find out whether there has been change in the situation since the initial study.
one carried out over a period of time so that chronological time has an opportunity to exert an effect as a variable.
see descriptive study (above).
one in which the data to be studied are yet to be generated, the events having not yet occurred.
one based on examination of existing data, on events that have already occurred.
one in which the real circumstances are simulated, either in fact, or by means of a set of mathematical formulae each of which expresses the probability of each outcome in a series of consequential events that mirror the possible pathways in a real-life situation.