Which study design follows exposed and non-exposed individuals over time to determine incidence of disease?

Which study design follows exposed and non-exposed individuals over time to determine incidence of disease?

• A. A case-control study
• B. A cross-sectional study
• C. A cohort study
• D. A clinical trial

Answer: (C)

This design focuses on measuring incidence by following groups over time based on exposure status. In a cohort study, you start with people who are exposed and a comparable group who are not exposed, then watch to see who develops the disease. Because you track new cases as they occur, you can directly calculate incidence and compare the risk between the exposed and unexposed groups. This approach also helps establish temporality—exposure precedes disease—which is essential for understanding cause-and-effect relationships. Cohort studies can be done prospectively, where you enroll participants and follow them forward, or retrospectively, using existing records to reconstruct exposure and outcomes. Other designs don’t follow exposed and non-exposed groups over time to measure new cases: case-control starts with people who have or don’t have the disease and looks back to determine exposure; cross-sectional assesses exposure and disease at a single moment, providing prevalence rather than incidence; a clinical trial assigns an intervention and follows outcomes, which is experimental rather than observational, though it also tracks events over time.

This design focuses on measuring incidence by following groups over time based on exposure status. In a cohort study, you start with people who are exposed and a comparable group who are not exposed, then watch to see who develops the disease. Because you track new cases as they occur, you can directly calculate incidence and compare the risk between the exposed and unexposed groups. This approach also helps establish temporality—exposure precedes disease—which is essential for understanding cause-and-effect relationships. Cohort studies can be done prospectively, where you enroll participants and follow them forward, or retrospectively, using existing records to reconstruct exposure and outcomes.

Other designs don’t follow exposed and non-exposed groups over time to measure new cases: case-control starts with people who have or don’t have the disease and looks back to determine exposure; cross-sectional assesses exposure and disease at a single moment, providing prevalence rather than incidence; a clinical trial assigns an intervention and follows outcomes, which is experimental rather than observational, though it also tracks events over time.