What is a major advantage of case-control studies?

Case-control studies are particularly advantageous because they are relatively fast and less expensive compared to other study designs, such as cohort studies or randomized controlled trials. This is primarily due to the way they are structured. In a case-control study, researchers start with individuals who have a specific disease (the cases) and compare them to individuals without the disease (the controls). This allows researchers to look back in time to assess exposures or risk factors associated with the disease.

The ability to focus on individuals already affected by the disease means that fewer resources are typically needed to collect data, as opposed to tracking large groups over time as in cohort studies. Moreover, because cases can be identified quickly and controls can often be matched from existing records or databases, researchers can gather results more promptly, thus allowing for quicker public health responses or interventions.

The other options highlight limitations or features that do not align with the advantages of case-control studies. For instance, they can indeed study rare diseases effectively, require smaller sample sizes than cohort studies, and are not inherently time-consuming.