Longitudinal Cohort Study

A Longitudinal Cohort Study is a longitudinal study that is a cohort-based study.

• AKA: Concurrent Study, Follow-up Study, Incidence Study, Prospective Study.
• Context:
  • It can range from being a Retrospective Cohort Study to being a Prospective Cohort Study.
  • It can be analyzed by Cohort Analysis.
  • …
• Counter-Example(s):
  • a Case Control Study.
• See: Cohort, Controlled Experiment.

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References

2013

• http://en.wikipedia.org/wiki/Cohort_study
  • A cohort study or panel study is a form of longitudinal study (a type of observational study) used in medicine, social science, actuarial science, business analytics, and ecology. It is an analysis of risk factors and follows a group of people who do not have the disease, and uses correlations to determine the absolute risk of subject contraction. It is one type of clinical study design and should be compared with a cross-sectional study. Cohort studies are largely about the life histories of segments of populations, and the individual people who constitute these segments.

    A cohort is a group of people who share a common characteristic or experience within a defined period (e.g., are born, are exposed to a drug or vaccine or pollutant, or undergo a certain medical procedure). Thus a group of people who were born on a day or in a particular period, say 1948, form a birth cohort. The comparison group may be the general population from which the cohort is drawn, or it may be another cohort of persons thought to have had little or no exposure to the substance under investigation, but otherwise similar. Alternatively, subgroups within the cohort may be compared with each other.

    Randomized controlled trials are a superior methodology in the hierarchy of evidence in therapy, because they limit the potential for any biases by randomly assigning one patient pool to an intervention and another patient pool to non-intervention (or placebo). This minimizes the chance that the incidence of confounding (particularly unknown confounding) variables will differ between the two groups. However, it is important to note that RCTs may not be suitable in all cases and other methodologies could be much more suitable to investigate the study's objective.

    Cohort studies can either be conducted prospectively, or retrospectively from archived records.

2009

• (Barratt & Kirwan, 2009) ⇒ Helen Barratt, and Maria Kirwan. (2009). “Cohort Studies: Design, Applications, Strengths & Weaknesses of Cohort Studies.” In: http://www.HealthKnowledge.org.uk
  • QUOTE: Cohort studies evaluate a possible association between exposure and outcome by following a group of exposed individuals over a period of time (often years) to see whether they develop the disease or outcome of interest. A cohort is a group of individuals who share a common characteristic, such as workers from the same factory. Participants are selected on the basis of exposure, and should be free of the outcome under investigation at the start of the study.

    The incidence of disease in the exposed group is then compared to the incidence of disease in an unexposed group, and a relative risk (incidence risk or incidence rate) is calculated to assess whether the exposure and disease are causally linked.

     Cohort studies may be prospective or retrospective, but both types define the cohort on the basis of exposure, not outcome.

2007

• http://www.statistics.com/resources/glossary/c/cohortstudy.php
  • A cohort study is a longitudinal study that identifies a population or large group (a "cohort") then draws a sample from the population at various points in time and records data for the sample.

• http://www.statistics.com/resources/glossary/l/longstudy.php
  • Longitudinal study: Longitudinal studies are those that record data for subjects or variables over time. If a longitudinal study uses the same subjects at each point where data are recorded, it is a panel study . If a longitudinal study samples from the same group at each point where data are recorded, it is a cohort study . See also longitudinal data, cross sectional study .

• US National Institute of Health. “IUPAC Glossary of Terms Used in Toxicology."
  • cohort study / concurrent study / follow-up study / incidence study / longitudinal study / prospective study:
    • Analytic study of epidemiological study in which subsets of a defined population can be identified who are, have been, or in the future may be exposed or not exposed, or exposed in different degrees, to a factor or factors hypothesized to influence the probability of occurrence of a given disease or other outcome. The main feature of the method is observation of a large population for a prolonged period (years), with comparison of incidence rates of the given disease in groups that differ in exposure levels.
  • cohort: Component of the population born during a particular period and identified by period of birth so that its characteristics (such as causes of death and numbers still living) can be ascertained as it enters successive time and age periods. The term “cohort” has broadened to describe any designated group of persons followed or traced over a period of time, as in the term cohort study (prospective study).
  • cohort analysis: Tabulation and analysis of morbidity or mortality rates in relationship to the ages of a specific group of people (cohort), identified by their birth period, and followed as they pass through different ages during part or all of their life span. In certain circumstances such as studies of migrant populations, cohort analysis may be performed according to duration of residence in a country rather than year of birth, in order to relate health or mortality experience to duration of exposure.

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