University of Central Florida (UCF) HSC4501 Epidemiology of chronic diseases Exam 1 Practice

For studying rare diseases or outcomes, starting with individuals who already have the disease and comparing them to similar individuals who do not is the most efficient approach. This case-control design allows you to assess past exposures quickly and with far fewer participants, which is especially important when the outcome is uncommon. Because you’re selecting based on disease status, you don’t need to wait for new cases to occur in a large population, making the study faster and cheaper. The measure you typically get is the odds ratio, which closely approximates the relative risk when the disease is rare.

In contrast, a prospective cohort would require enrolling a large number of people and following them over time to accumulate enough incident cases, which becomes impractical and costly for rare outcomes. Ecological studies examine populations rather than individuals, so they can’t reliably establish exposure-disease relationships at the individual level. Randomized trials, while powerful, are often not feasible for rare diseases due to the large required sample sizes and ethical considerations around randomizing exposure in small or affected groups.