cohort study

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Related to Cohort studies: panel studies


a careful examination of a phenomenon; see also design.
cohort study prospective 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.
flow study uroflowmetry.
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 study uroflowmetry.
voiding pressure study simultaneous measurement of bladder contraction, urinary flow, and sphincter electromyogram.

co·hort stud·y

a study using epidemiologic methods, such as a clinical trial, in which a cohort with a particular attribute (for example, smokers, recipients of a drug) is followed prospectively and compared for some outcome (for example, disease, cure) with another cohort that does not possess that attribute.
Synonym(s): follow-up study (1)

cohort study

(in research) a study concerning a specific subpopulation, such as the children born between December and May in 1975 or those born in the same months in 1955. See also prospective study.

cohort study

An observational study in which a defined group of people (a cohort) is followed over time and outcomes are compared in subsets of the cohort who were exposed, not exposed, or exposed at different levels to an intervention or other factor of interest. Cohorts can be assembled in the present and followed into the future (a “concurrent cohort study”), or identified from past records and followed from that time up to the present (a “historical cohort study”). Because random allocation is not used, matching or statistical adjustment must be used to ensure that the comparison groups are as similar as possible.
References in periodicals archive ?
The existence of two highly comparable cohort studies so conveniently spaced provided the authors with the opportunity to help answer, among other questions, what impact legislative actions have on increasing pay equality between men and women.
Data Source: Data came from a meta-analysis of four studies with a total of 2,447 RA patients, and from a comparison of two prospective cohort studies with a total of 828 RA patients.
The authors of this systematic review of cohort studies undertook to clarify the benefits of fruit and vegetable consumption in relation to cognitive decline and dementia.
This well-done meta-analysis supports these findings: for the more-reliable prospective cohort studies (rather than case-control studies) the current study finds a 29 percent lower risk for subjects in the highest category of alcohol consumption in comparison with subjects in the lowest alcohol category.
Two population-based retrospective cohort studies (7,8) among Lyme disease patients whose illness was diagnosed in the mid-1980s determined that one third to half had clinically corroborated post-Lyme syndrome symptoms years after the initial onset of disease.
prospective cohort studies, in which researchers collect diet information from a large group of healthy people, wait several years, and then compare the diets of those who developed cancer in the interim to those who did not.
Many observational cohort studies have shown that moderate alcohol use is associated with better cognitive function.
Of 18 cohort studies of women who were occupationally exposed to asbestos, all but one study reported standardized mortality ratios (SMRs) comparing observed numbers of deaths with expected numbers for the general population.
DENVER -- Use of nonaspirin NSAIDs more than twice per week was associated with a 45% reduction in the risk of developing bladder cancer in a pooled analysis of three prospective cohort studies totaling more than half a million subjects.
conducted a meta-analysis of 5 case-control studies and 10 cohort studies.
Real-world information on the impact of HAART in daily practice comes from what are known as cohort studies, which follow the experiences of specific groups of patients over extended periods of time.