Fundamental Difference Between Cohort Method and Randomized Controlled Trial
A cohort study alludes to a study design where one or more samples, typically alluded to as cohorts are followed prospectively, and subsequent evaluation of status with respect to an outcome or disease is undertaken in a bid to ascertain which initial participants exposure traits are associated with it. Therefore, as the study is undertaken, the outcomes from the participants in each cohort are evaluated, and the connections with certain traits are ascertained (Cohort Study, 2019). This method is usually the best for the measurement of the effects of a suspected risk factor where the researchers raise questions and formulate hypotheses about the potential causes of disease. Randomized Controlled Trials (RCTs), on the contrariwise, are study designs that randomly assigns participants into an experimental or control group, and as it is undertaken, the only expected difference between the two groups is the outcome variable under study. RCTs are usually considered as the best and most rigorous means of investigating interventional medications, like new drugs, but it is not possible to utilize them to test the causes of the disease, and this is the main difference between RCTs and cohort studies. Another significant difference is that the intervention in RCT is controlled by the investigator, while the interventions in cohort studies are usually a naturally occurring process (Glasser, 2008). This means that in cohort studies, the researchers typically observe what is happening without intervention, while in RCTs, the researchers intervene, for instance, by giving the participants a new drug and evaluating the outcomes (Legg, 2018).
Advantages and Disadvantages of Cohort Studies
A major advantage of cohort studies is the capacity to study a myriad of outcomes that can be linked with a single exposure or several exposures in a specific study. Besides, the combined impact of multiple exposures on the outcome can be determined. Another advantage is that it allows the researchers to study rare exposures as they are capable of explicitly selecting subjects that are exposed to a specific factor. In addition, cohort studies usually have broader inclusion as well as fewer exclusion criteria in contrast to other study methods such as randomized controlled trials. Similarly, the investigators are capable of obtaining large samples and thus attain substantial power in statistical analyses in contrast to RCTs. Furthermore, the longitudinal nature of cohort studies translates to the fact that variations in exposure levels can be measured in a bid to provide an insight into the dynamic nature between exposure and outcome.
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One of the significant disadvantages of cohort studies is that it is susceptible to loss to follow-up in contrast to cross-sectional studies. Similarly, confounding variables are one of the major problems in cohort studies, especially in regards to the data analysis compared to RCTs (Wang and Kattan, 2020). In addition, the fact there are no randomizations means that imbalances in patient characteristics could be present. The outcome of interest in cohort studies also take time to occur, and masking and binding are also challenging.
Characteristics of a Correlational Study
Correlational studies are non-experimental methods of research that do not involve the manipulation of the independent variable. In this study, the researchers usually study the relationships between one or more quantitative independent variables and one or more quantitative dependent variables. Some of the characteristics of correlational studies include:
They are non-experimental - correlational research is non-experimental since it does not entail the manipulation of variables using a scientific method in a bid to disagree or agree with a hypothesis. Therefore, the researcher observes and measures the relationship between two variables without subjecting them to any conditions.
They are backward-looking- correlational research usually does not consider the future as it only entails the measurement and observation of the recent historical relationship between two variables. In this manner, the statistical patterns which result from correlational studies are backward-looking and can seize to exist at any given point.
It is dynamic- statistical patterns that exist between two variables are ever-changing, and thus they cannot be utilized as a standard value for further research. This means that data which result from correlational studies is not consistent or constant and therefore cannot be used in other research as a standard.
Cohort Studies in Research Pyramids
The research pyramid is a representation of how evidence move up both in generalizability and credibility, and there have been different versions produced to showcase the progressions. According to Ingham-Broomfield (2016), Cohort Studies are on the 5 th level of the comparative grid of the seven levels of evidence meaning that they are more reliable than case-controlled studies and background information or expert opinion. However, they are less reliable than random control trials, critically-appraised individual articles, critically appraised topics, and systematic reviews and meta-analyses.
The significance of the research pyramid is that it helps one in identifying the levels of research that are more reliable. It also provides a means of visualizing both the amount of evidence that is available as well as the quality of evidence, meaning that those that are at the lower levels of the pyramid are abundant and less reliable while those on the higher regions of the pyramid are scarce but are highly reliable. Therefore, as one goes down the pyramid, the number of evidence increases, but the quality of the evidence declines. The pyramid is used by researchers and professionals to have an understanding of how reliable and dependable a type of study is when undertaking their studies and is thus important.
References
Cohort Study. (2019). Retrieved 15 March 2021, from https://himmelfarb.gwu.edu/tutorials/studydesign101/cohorts.cfm
Glasser, P. (2008). Essentials of clinical research . S. P. Glasser (Ed.). Springer.
Ingham-Broomfield, R. (2016). A nurses' guide to the hierarchy of research designs and evidence. Australian Journal of Advanced Nursing, The , 33 (3), 38.
Legg, J. T. (2018). What is a cohort study in medical research? Retrieved 15 March 2021, from https://www.medicalnewstoday.com/articles/281703
Wang, X., & Kattan, M. W. (2020). Cohort studies: Design, analysis, and reporting. Chest , 158 (1), S72-S78.
