Certified in Public Health (CPH) Practice Exam

What is the relationship between cohort studies and their measures of association?

1. Cohort study is to cumulative incidence as case-control study is to odds ratio.

2. Cohort study is to cross-sectional study as case-control study is to rate ratio.

3. Cohort study is to risk ratio as case-control study is to odds ratio.

4. Cohort study is to incidence density as case-control study is to prevalence.

The correct answer is: Cohort study is to risk ratio as case-control study is to odds ratio.

In public health research, the relationship between study designs and their respective measures of association is crucial for understanding how exposure and outcome relationships are quantified. Cohort studies are particularly valuable because they allow researchers to observe the development of outcomes over time among individuals who are exposed and those who are not exposed to a particular factor. The risk ratio, also known as the relative risk, is a measure used in cohort studies to compare the probability of an outcome occurring in the exposed group to that in the unexposed group. It provides direct data on how exposure affects the risk of developing a condition, making it a suitable and direct measure of association for cohort studies. On the other hand, case-control studies, which assess individuals already affected by the outcome (cases) compared to those without (controls), use the odds ratio to measure association. The odds ratio compares the odds of exposure in cases to the odds of exposure in controls. This is particularly useful in case-control studies since they often look backwards at exposures rather than following individuals over time. In summary, the correct association—specifically linking cohort studies with the risk ratio and case-control studies with the odds ratio—highlights how each study design fits with its appropriate measure of effect to best analyze and interpret epidemiological data