Cohort Study: From 3 Different Sources
A systemised follow-up study of people for a speci?c period of time, or until the occurrence of a de?ned event such as a particular illness or death. The aim is to follow the disease course and/or the reasons for the participants’ deaths. Di?erent cohorts may be compared and conclusions drawn about a particular disease or drug treatment.
An observational study in which outcomes in a group of participants that received an intervention are compared with outcomes in a similar group (i.e. the cohort) of participants, either contemporary or historical, that did not receive the intervention. In an adjusted (or matched) cohort study, investigators identify (or make statistical adjustments to provide) a cohort group that has characteristics (e.g. age, gender, disease severity) that are as similar as possible to the group that experienced the intervention.
a *longitudinal study of a group of people defined by some common characteristic (typically age). It may be conducted prospectively or retrospectively. A prospective cohort study involves a systematic follow-up for a defined period of time or until the occurrence of a specified event (e.g. onset of illness, retirement, or death) in order to observe patterns of disease and/or cause of death. A retrospective cohort study examines data relating to the group’s history of exposure and disease experience.
A study that starts with the identification of persons with the disease (or other outcome variable) of interest, and a suitable control (comparison, reference) group of persons without the disease. The relationship of an attribute to the disease is examined by comparing the diseased and non-diseased with regard to how frequently the attribute is present or, if quantitative, the level of the attribute, in each of the groups.... case control study
See “cohort study”.... prospective study
A research design used to test hypotheses in which inferences about exposure to the putative causal factor(s) are derived from data relating to characteristics of the persons under study or to events or experiences in their past. The essential feature is that some of the persons under study have the disease or other outcome condition of interest, and their characteristics and past experiences are compared with those of other, unaffected persons.... retrospective study
A study that measures the prevalence of health outcomes or determinants of health, or both and other variables of interest in a population at a point in time or over a short period.... cross-sectional study
Comparison of outcomes between two or more groups of patients who have been intentionally given di?erent treatments or preventative measures, for example, diets. The subjects in the trial should be randomly allocated to the groups, with patients in one group – called controls – receiving no active treatment. If possible, neither patients nor doctors participating in a study should know which patients are receiving what treatment (double blind study/trial). Furthermore, groups should exchange treatments after a prearranged time (crossover study/trial). (See CLINICAL TRIALS; RANDOMISED CONTROLLED TRIAL.)... intervention study
A study designed to examine associations, commonly putative or hypothesized causal relationships. An analytic study is usually concerned with identifying or measuring the effect of risk factors, or is concerned with the health effects of specific exposure(s).... analytic study
An in-depth study of an individual, group, institution, organization or programme. The advantage of the case study method is that it allows more intensive analyses of specific empirical details. However, it is difficult to use the results to generalize to other cases.... case study
A set of people born during a specific time period; also a set of people born during a historical era that creates different inter-cohort characteristics such as size, composition, experiences and values. The term “cohort” has been broadened to describe any designated group of persons who are followed or traced over a period of time.... cohort
A study concerned with and designed only to describe the existing distribution of variables, without regard to causal or other hypotheses.... descriptive study
A study in which conditions are under the direct control of the investigator.... experimental study
A study where the main objective is to explain, rather than merely describe, a situation by isolating the effects of specific variables and understanding the mechanisms of action.... explanatory study
Preliminary study to determine the practicability of a proposed health programme or procedure, or of a larger study, and to appraise the factors that may influence its practicability.... feasibility study
A study in which individuals or populations, selected on the basis of whether they have been exposed to risk, have received a specified preventive or therapeutic procedure, or possess a certain characteristic, are followed to assess the outcome of exposure, the procedure or the effect of the characteristic, e.g. occurrence of disease.... follow-up study
See “synthetic study”.... integrative study
A study in which the investigators do not manipulate the use of an intervention (e.g. do not randomize people to treatment and control groups) but only observe people who are (and sometimes people who are not) exposed to the intervention, and interpret the results.... observational study
A study, generally undertaken by an individual health programme or health planning agency to determine the geographic distribution of the residences of the patients served by one or more health programmes. Such studies help define catchment and medical trade areas and are useful in locating and planning the development of new services.... patient-origin study
A small-scale test of the methods and procedures to be used on a larger scale if the pilot study demonstrates that these methods and procedures can work.... pilot study
See “cross-sectional study”.... prevalence study
An investigation that collects original (primary) data from subjects, e.g. randomized controlled trials, observational studies, series of cases, etc. See “secondary data analysis”.... primary study
A study that does not generate primary data but that involves the qualitative or quantitative consolidation of findings from multiple primary studies. Examples are literature review, meta-analysis, decision analysis and consensus development.... synthetic study
Identification of species and their genetic relationship to one another.... taxonomic study
a combined X-ray and manometry examination of the bladder to look for abnormal function. The bladder is filled slowly with contrast medium using a small urinary catheter and the pressure is monitored during filling and voiding (micturition). X-ray images of the bladder and urethra (see urethrography) are taken. The test is used to differentiate between obstruction to bladder outflow and abnormal involuntary contractions of the muscle in the bladder wall.... bladder pressure study
(EPS) an assessment of the electrical system of the heart by means of thin preshaped wires passed into the heart via the femoral vein. An *electrocardiogram is recorded from various points within the heart, and the reaction of the heart to timed electrical stimuli is observed. The information obtained guides treatment of arrhythmia, particularly *radiofrequency ablation.... electrophysiological study
the collection and analysis of data about a group of participants over a period of time, often some years. Compare cross-sectional study. See also cohort study.... longitudinal study
see case control study.... matched pair study
a test done to assess the peripheral nervous system. It involves activating the nerves electronically with electrical pulses and measuring the responses obtained.... nerve conduction study
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