Question

Compare and contrast between Case control and Cohort study.

Hint:

Case-control studies are best for rare diseases, while cohort studies are more effective for understanding risk factors and disease progression over time.

Answer 1

Step 1: Case control study. 
In a case-control study, participants are selected based on the presence (cases) or absence (controls) of a particular disease or condition. The study aims to determine the exposure to a risk factor or association with the disease by comparing the two groups. This is a retrospective study design, meaning the data is collected after the outcome has occurred. Key features include: 
- Retrospective design: Studies are based on past exposures and conditions. 
- Use of control group: A group without the disease is compared to the case group with the disease. 
- Efficiency: Ideal for studying rare diseases. 
- Limitations: Prone to recall bias and cannot establish causality. 
 

Step 2: Cohort study. 
In a cohort study, participants are grouped based on exposure to a risk factor and followed over time to observe the development of outcomes. This can be either prospective (looking forward) or retrospective (looking back). Key features include: 
- Prospective design: Follows a group over time to observe outcomes. 
- Focus on exposure: Participants are grouped by exposure to a risk factor, then tracked for the development of disease. 
- More reliable: Can establish temporal relationships and is less prone to bias compared to case-control studies. 
- Limitations: Expensive and time-consuming, especially for rare diseases. 
 

Step 3: Comparison. 
\[\begin{array}{|l|l|l|} \hline \textbf{Aspect} & \textbf{Case-Control Study} & \textbf{Cohort Study} \\ \text{Study Type} & \text{Retrospective} & \text{Prospective or Retrospective} \\ \hline \text{Focus} & \text{Outcome (disease or condition)} & \text{Exposure to risk factors} \\ \hline \text{Time Frame} & \text{Past exposures} & \text{Future outcomes} \\ \hline \text{Efficiency} & \text{Suitable for rare diseases} & \text{Suitable for common diseases} \\ \hline \text{Bias} & \text{Prone to recall bias} & \text{Less prone to bias} \\ \hline \end{array}\]