A cohort study is a special form of longitudinal research that takes a sample of groups (a group of people who share defining characteristics, usually those who experience a general event in a chosen period, such as birth or graduation), cross- time interval. While cohort studies are panel studies, panel studies are not always cohort studies because individuals in panel studies do not always have the same characteristics.
The cohort study is one of the basic epidemiological designs used in research in medicine, nursing, psychology, social sciences, and in any field that depends on 'stateless' statements of 'inextricable' answers. In medicine for example, while clinical trials are used primarily to assess the safety of newly developed drugs before they are approved for sale, an epidemiological analysis of how risk factors influence disease events is often used to identify the cause of the disease in the first place, and to help provide pre-clinical justification to make sense of the protective factor (care). The cohort study differs from clinical trials because there is no intervention, treatment, or exposure given to participants in the cohort design; and no control group is specified. In contrast, cohort studies are largely about the life history of the population segment, and the individual individuals that make up this segment. Exposure or protective factors are identified as characteristics of pre-existing participants. This study was controlled by incorporating other common characteristics of cohorts in statistical analyzes. Both exposure/treatment and control variables are measured at baseline. Participants are then followed from time to time to observe the degree of disease or outcome in question. Regression analysis can then be used to evaluate the extent to which exposure or treatment variables contribute to the incidence of the disease, while accounting for other variables that may play.
Double-blind randomized controlled trials (RCTs) are generally considered to be superior methodologies in the hierarchy of evidence in treatment, as they allow for most control over other variables that can affect outcomes, and randomization and dazzling processes reduce bias in the study design. This minimizes the likelihood that the results will be affected by confounding variables, especially the unknown. However, hypotheses based on prior research and background knowledge are used to select the variables to be included in the regression model for cohort studies, and statistical methods can be used to identify and take into account potential confounders of these variables. Biases can also be mitigated in cohort studies when selecting participants for cohorts. It is also important to note that RCT may not be suitable in all cases; as when the outcome is a negative health effect and its exposure is hypothesized to be a risk factor for the outcome. Ethical standards, and morality, will prevent the use of risk factors in RCTs. This natural or incidental exposure to these risk factors (eg, time spent in the sun), or self-administered exposure (eg smoking), can be measured without subjecting participants to risk factors outside the lifestyle, habits, and choice of each.
Cohort studies can be retrospective (looking backward, so using existing data such as medical records or claims databases) or prospective (requiring new data collection). The retrospective cohort study limits the researcher's ability to reduce assimilation and bias because the information collected is limited to existing data. However, there are advantages to this design, because retrospective studies are much cheaper and faster because data has been collected and stored.
A cohort is a group of people who share common characteristics or experience within a prescribed period (for example, currently living, exposed to drugs or vaccines or pollutants, or undergoing certain medical procedures). So a group of people born on a day or at a certain period, say 1948, form a birth group. The comparison group may be the general population from which the cohort is taken, or perhaps another group considered to have little or no exposure to the substance under study, but on the contrary similar. Alternatively, subgroups in cohorts can be compared with each other.
Indicators of cohort studies:
- When there is a strong relationship between cause and effect, set by each observational study
- When exposure is rare, but the incidence of the disease among exposed is high
- When someone's attention can be minimized
- When resources are sufficient
Video Cohort study
Apps
In medicine, cohort research is often done to obtain evidence to try to deny the existence of suspected associations between cause and effect; failure to deny the hypothesis often reinforces the belief in it. Importantly, the cohort was identified before the onset of the disease under study. The study group follows a group of people who do not have the disease for an extended period of time and see who develops the disease (a new incident). Therefore the group can not be defined as a group of people who already have the disease. A prospective (longitudinal) cohort study between exposure and disease is helpful in studying causal relationships, although distinguishing true causality usually requires further proof of further experimental experiments.
The advantage of prospective cohort study data is that it can help determine risk factors for contracting new diseases due to longitudinal observation of individuals through time, and data collection on a regular basis, so that recall errors are reduced. However, cohort studies are expensive to do, are sensitive to attrition and take long follow-up time to generate useful data. Nevertheless, results obtained from long-term cohort studies have far superior quality than those obtained from retrospective/cross-sectional studies. A prospective cohort study is considered to produce the most reliable results in observational epidemiology. They allow various disease-exposure associations to be studied.
Several study groups tracked groups of children since their birth, and recorded various information (exposure) about them. The value of cohort studies depends on the ability of the researcher to stay in touch with all cohort members. Some research has been going on for decades.
In a cohort study, the population studied consisted of individuals at risk of developing a particular disease or health outcome.
Maps Cohort study
Example
An example of an epidemiological question that can be answered using a cohort study is whether X exposure (say, smoking) is associated with Y results (eg, lung cancer). In 1951 started the British Physician Study, a group that included smokers (exposed groups) and nonsmokers (unexposed groups). This study continued until 2001. In 1956, this study provided compelling evidence of smoking associations with the incidence of lung cancer. In the cohort study, these groups were matched in terms of many other variables such as economic status and other health status so that the variables being assessed, the independent variables (in this case, smoking) could be isolated. as the cause of the dependent variable (in this case, lung cancer). In this example, a statistically significant improvement in the incidence of lung cancer in the smoking group compared with the non-smoking group is evidence supporting the hypothesis. However, rare outcomes, such as lung cancer, are generally not studied using cohort studies, but are rather studied using case-control studies.
Short-term research is commonly used in medical research as a form of clinical trials, or a means to test certain hypotheses about clinical importance. Such studies usually follow two groups of patients for a certain period of time and compare the size of the endpoint or outcome between the two groups.
Randomized controlled trials, or RCTs are superior methodologies in the hierarchy of evidence, as they limit the bias potential by randomly assigning one pool of patients to intervention and another pool of patients for non-intervention (or placebo). This minimizes the likelihood that the incidence of confounding variables will differ between the two groups.
However, it is sometimes impractical or ethical to conduct RCTs to answer clinical questions. To take our example, if we already have reasonable evidence that smoking causes lung cancer and then persuades a group of non-smokers to smoke to test this hypothesis will generally be considered very unethical.
Two examples of cohort studies that have lasted for more than 50 years are the Framingham Heart Study and National Child Development Study (NCDS), the most widely researched from the UK-born cohort study. The main findings of NCDS and the detailed profiles of this study appear in the International Journal of Epidemiology .
The Dunedin Longitudinal Study, started in 1975, has studied a thousand people born in Dunedin, New Zealand in 1972-73. Subjects were interviewed on a regular basis, with Phase 45 beginning in 2017.
The largest cohort study in women was the Nurses' Health Study. Started in 1976, it tracked more than 120,000 nurses and has been analyzed for a variety of different conditions and outcomes.
The largest cohort study in Africa is the Birth to Twenty Study, which began in 1990 and tracked a group of more than 3,000 children born in the weeks after Nelson Mandela was released from prison.
Another notable example is the Grant Study which tracks a number of Harvard graduates from ca. 1950,77, the Whitehall Study tracked 10,308 British civil servants, and the Caerphilly Heart Disease Study, which since 1979 has studied representative samples of 2,512 men, taken from the town of Welsh, Caerphilly.
Variations
The diagram shows the starting point and direction of the cohort study and case-control studies. In case-control studies, the results of analyzes of documented illnesses and investigations were conducted to arrive at possible causes of the disease. In a cohort study, the assessment began with a suspected cause of the disease, and observations were made of disease events associated with hypothesized causative agents .
Current and historical cohorts
The current cohort study is a true prospective study in which data on exposure is assembled before the facts to be learned, such as disease. An example of the current cohort study is the Oxford Family Planning Association Study in the UK, which aims to provide a balanced view of the beneficial and harmful effects of various contraceptive methods. This study has provided a large amount of information on the efficacy and safety of contraceptive methods, and in particular oral contraceptives (oral contraceptives), diaphragms and intrauterine devices (IUDs).
In a historical cohort study, data on exposure and incidence of disease, birth, political attitudes or other category variables were collected after the event occurred, and subjects (exposed and unexposed to the investigating agency) were assembled from existing records or health care lists.
A "prospective cohort" defines the group before the study is conducted, while historical studies, sometimes referred to as "retrospective cohorts", define grouping after data is collected. An example of a retrospective cohort is the Long Term Mortality after Gastric Bypass Surgery and The Lothian Birth Cohort Studies.
Although historical study is sometimes referred to as a retrospective study, it is a misnomer because the methodological principles of historical cohort studies and prospective studies are the same.
Nested case-control case
An example of a case-control study is the inflammatory markers and risk of coronary heart disease in men and women, which is a case-control analysis extracted from the Framingham Heart study group.
Household panel survey
Household panel surveys are an important sub-type of cohort study. It describes representative household samples and surveys them, following all individuals from time to time on an annual basis. Examples include the US Panel of Studies on Revenue Dynamics (since 1968), the German Economic Social Panel (since 1984), the UK Household Panel Survey (since 1991), Households, Income and Employment Dynamics in the Australian Survey (since 2001) and the House Panel Ladder of the European Community (1994-2001).
Cohort analysis in business
For an example in business analysis, see cohort analysis.
See also
- Panel analysis
- Panel data
- Cohort (statistics)
References
External links
- Candidate candidate
- Retrospective cortex
- Cornell University College of Veterinary Medicine Design Tutorial Tutorial
- Chronicle schedule of birth study (ESDS Longitudinal)
- Longitudinal Study Center
Source of the article : Wikipedia
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