Which is a common disadvantage of case-control studies?

Which is a common disadvantage of case-control studies?

• A. They are expensive and time-consuming.
• B. They are prone to recall bias and selection bias; cannot directly measure incidence.
• C. They require randomization.
• D. They can only study rare exposures.

Answer: (B)

Case-control studies look back in time from disease status to past exposures, which makes them efficient for studying rare diseases but introduces diagnostic and design biases. The central limitation is that exposure data are collected after the fact, often relying on memory or records, so recall bias can distort the association—cases may overestimate or misreport exposures compared to controls. Selection bias is another risk: if controls aren’t drawn from the same population that would have become cases, the comparison isn’t valid. Plus, because you start with disease status and don’t follow people over time, you can’t directly measure incidence or risk; you typically calculate an odds ratio, which only approximates relative risk when the disease is rare. These biases and the lack of direct incidence measurement are the main disadvantages of case-control designs. Randomization is not inherent to this design (it’s a feature of randomized trials), and case-control studies are often chosen because they’re efficient for studying rare diseases, not because they’re limited to rare exposures.

Case-control studies look back in time from disease status to past exposures, which makes them efficient for studying rare diseases but introduces diagnostic and design biases. The central limitation is that exposure data are collected after the fact, often relying on memory or records, so recall bias can distort the association—cases may overestimate or misreport exposures compared to controls. Selection bias is another risk: if controls aren’t drawn from the same population that would have become cases, the comparison isn’t valid. Plus, because you start with disease status and don’t follow people over time, you can’t directly measure incidence or risk; you typically calculate an odds ratio, which only approximates relative risk when the disease is rare. These biases and the lack of direct incidence measurement are the main disadvantages of case-control designs. Randomization is not inherent to this design (it’s a feature of randomized trials), and case-control studies are often chosen because they’re efficient for studying rare diseases, not because they’re limited to rare exposures.