What is the Difference Between Case Control and Cohort Study

The main difference between case control and cohort study is that case-control studies are retrospective while cohort studies can be either prospective or retrospective. Moreover, case-control studies usually proceed from the effects of a disease to its cause while cohort studies proceed from the cause of a disease to its effects.

Case-control studies and cohort studies are two types of scientific research studies that analyze the causes of studies. Researchers use both these studies to analyze the effects and causes of diseases and to determine risk factors and incidence of diseases.

Key Areas Covered

1. What is a Case-Control Study
     – Definition, Design
2. What is a Cohort Study
     – Definition, Features, Design
3. What is the Difference Between Case Control and Cohort Study
     – Comparison of Key Differences

Key Terms

Case Control Study, Cohort Study, Longitudinal Study

What is a Case Control Study

A case-control study is a type of observational study where researchers identify two groups differing in outcomes and compare them on the basis of some supposed causal attribute. Moreover, this type of study is mainly used in the field of health and medicine to identify factors that may contribute to medical conditions. For example, a medical research study may compare patients who have a certain disease with patients who don’t have that disease to observe and compare how frequently the exposure to a risk factor is present in each group. This will help to determine the relationship between the risk factor and the disease.

Thus, the case-control studies are ideal for researching rare conditions or diseases. Since the medical condition or disease has already occurred in the sample, these studies require less time. In addition to these, case-control studies let the researchers investigate multiple risk factors simultaneously.

What is a Cohort Study

A cohort study is a type of longitudinal study that observes the causes of disease and investigate the relationship between risk factors and health outcomes. Here, the term, cohort, itself refers to a group of people; a cohort study typically involves a large group of people. In a cohort study, the researcher records the sample populations’ exposure to particular risk factors in order to investigate the possible causes of the disease.

Furthermore, cohort studies can be prospective (forward-looking) or retrospective (backwards-looking). Prospective studies involve a lot of planning and may take place over several years. In this type of study, researchers attempt to form a hypothesis about the cause of a study and then observe a group of people over a period of time. Moreover, this group of people is actually known as a cohort; the researchers collect data from the cohort about the disease. Here, the researchers’ goal is to detect the changes in health-related to the possible risk factors they have identified. Retrospective cohort studies, on the other hand, observe data that already exist and attempt to identify risk factors for particular health conditions.

Difference Between Case Control and Cohort Study

Definition

A case-control study is an observational study that compares two groups of people: those with the disease under study as well as a very similar group of people who do not have the disease. A cohort study, on the other hand, is a type of longitudinal study that observes the causes of disease and investigate the relationship between risk factors and health outcomes.

Nature

Case-control studies are retrospective, while cohort studies can be either prospective or retrospective.

Cause and Effects of Diseases

Moreover, case-control studies usually proceed from the effects of a disease to its cause, while cohort studies proceed from the cause of a disease to its effects.

Sample

Cohort studies require a larger sample (a larger group of people) than case-control studies.

Time

In addition to these, cohort studies take a longer time period (sometimes several years) to conduct when compared to case-control studies.

Rare Diseases

Case-control studies are ideal for researching rare conditions or diseases, but cohort studies are not.

Conclusion

Case-control studies are retrospective studies that involve two groups of people: those with the disease as well as a similar group who don’t have the disease. Moreover, they are less expensive and takes less time to conduct. Cohort studies, on the other hand, can be either prospective or retrospective. They require a larger sample and may take a long time, sometimes even several years. Thus, this is the difference between case control and cohort studies.

Reference:

1. “Cohort Study: Finding Causes, Examples, and Limitations.” Medical News Today, MediLexicon International, Available here.
2. “Case–Control Study.” Wikipedia, Wikimedia Foundation, 22 July 2020, Available here.

Image Courtesy:

1. “GWAS is a case-control study” By Khanhhoa22 – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “ExplainingCaseControlSJW-en” By Jmarchn – File:ExplainingCaseControlSJW.jpg from Kelidimari (CC BY-SA 3.0) via Commons Wikimedia