Which study type typically uses odds ratios as its measure of association?

Which study type typically uses odds ratios as its measure of association?

• A. Cohort studies
• B. Cross-sectional studies
• C. Case-control studies
• D. Randomized trials

Answer: (C)

In case-control studies, you start with people who have the disease (cases) and those without it (controls) and look back to each group’s exposure history. Because the study design fixes the outcome first, you don’t observe incidence or risk in the population, so relative risk isn’t directly estimable. Instead, the natural measure to compare is the odds ratio, which looks at the odds of exposure among cases versus controls. The odds ratio is particularly central because it aligns with how data are collected in this design and can approximate relative risk when the disease is rare. In contrast, cohort studies or randomized trials focus on incidence and typically report risk or rate measures, not odds ratios, making this design the one where odds ratios are standard.

In case-control studies, you start with people who have the disease (cases) and those without it (controls) and look back to each group’s exposure history. Because the study design fixes the outcome first, you don’t observe incidence or risk in the population, so relative risk isn’t directly estimable. Instead, the natural measure to compare is the odds ratio, which looks at the odds of exposure among cases versus controls. The odds ratio is particularly central because it aligns with how data are collected in this design and can approximate relative risk when the disease is rare. In contrast, cohort studies or randomized trials focus on incidence and typically report risk or rate measures, not odds ratios, making this design the one where odds ratios are standard.