longitudinal study

study

[stud´e] 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.

lon·gi·tu·di·nal stud·y

a study of the natural course of life or disorder in which a cohort of subjects is serially observed over a period of time and no assumptions need be made about the stability of the system. Synonym(s): diachronic study

longitudinal study

An epidemiologic study that follows a population forward over time, evaluating the effects of one or more variables on a process. If individuals are followed, it is termed a longitudinal cohort study. If classes—e.g., age classes—are studied, it is a longitudinal cross-sectional study. Longitudinal studies are the converse of horizontal studies.

Examples
Cohort studies; case-control studies; Framingham Study in Massachusetts, US; Port Pirie study, an ongoing analysis of the long-term effects of blood lead levels on IQ.

longitudinal study

Diachronic study Statistics A study that follows the same persons over time, evaluating the effects of one or more variables on a processtime Examples Cohort studies, case-control studies. Cf Cross-sectional study, Horizontal study.

lon·gi·tu·di·nal stud·y

(lonji-tūdi-năl stŭdē) A study of the natural course of life or disorder in which a cohort of subjects is serially observed over a period of time and no assumptions need be made about the stability of the system.

单词	longitudinal study
释义	DictionarySeestudy longitudinal study longitudinal study [‚län·jə‚tüd·ən·əl ′stəd·ē] (psychology) The study of a group of individuals at regular intervals over a relatively long period of time. longitudinal study an investigation which involves making observations of the same group at sequential time intervals. Thus, a longitudinal study of a COHORT of children may be made to assess, for example, the effect of social class on school achievement (see BIRTH COHORT STUDY). Longitudinal studies are used by the National Children's Bureau to document various aspects of children's development in the UK. However, longitudinal studies are not only appropriate for studying human development or change, they may also be used to observe change over time within organizations. The advantage of longitudinal studies compared with CROSS-SECTIONAL STUDIES is that the causal factor involved in a sequence of changes an be directly explored using data collected before and after changes (e.g. analysis of the effect of changes in the school curriculum). The main disadvantages are the greater expense of repeated study, the possible HAWTHORNE EFFECT of repeated studies and the influence of other changes which may be occurring concurrently (e.g. changes in the school curriculum may take place at the same time as changes in the resourcing of educational services). Compare PANEL STUDY. longitudinal study study [stud´e] 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. lon·gi·tu·di·nal stud·y a study of the natural course of life or disorder in which a cohort of subjects is serially observed over a period of time and no assumptions need be made about the stability of the system. Synonym(s): diachronic study longitudinal study An epidemiologic study that follows a population forward over time, evaluating the effects of one or more variables on a process. If individuals are followed, it is termed a longitudinal cohort study. If classes—e.g., age classes—are studied, it is a longitudinal cross-sectional study. Longitudinal studies are the converse of horizontal studies. Examples Cohort studies; case-control studies; Framingham Study in Massachusetts, US; Port Pirie study, an ongoing analysis of the long-term effects of blood lead levels on IQ. longitudinal study Diachronic study Statistics A study that follows the same persons over time, evaluating the effects of one or more variables on a processtime Examples Cohort studies, case-control studies. Cf Cross-sectional study, Horizontal study. lon·gi·tu·di·nal stud·y (lonji-tūdi-năl stŭdē) A study of the natural course of life or disorder in which a cohort of subjects is serially observed over a period of time and no assumptions need be made about the stability of the system.
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