What is an advantage of a case-control study over a cohort study?

• A. A case-control study is less time consuming and less expensive.
• B. It provides direct incidence rates.
• C. It eliminates recall bias.
• D. It establishes temporal relationships more clearly.

Answer: (A)

The main concept here is the efficiency of case-control studies. Case-control studies start with people who already have the disease (cases) and a comparison group without the disease (controls), then look back to assess past exposures. This setup lets you study associations quickly and with fewer resources because you don’t have to follow a large disease-free population over time to see who develops the disease. This is especially advantageous when the disease is rare or when time and cost are limiting factors.

That efficiency is the key reason this design is preferable to a cohort study in many situations. However, note that case-control studies don’t provide direct incidence or risk estimates, can be affected by recall and selection biases, and are less able to establish temporality as clearly as cohort studies.