Cross-sectional studies are best defined as what type of study?

• A. Observational studies where exposure and outcome are measured at different times.
• B. Cohort studies where participants are followed to observe new cases.
• C. Observational studies where exposure and outcome are measured at the same time; can only measure prevalence.
• D. Experimental studies that assign exposures to participants.

Answer: (C)

Cross-sectional studies capture a snapshot in time by measuring both exposure status and health outcome at roughly the same moment. This makes them observational and well-suited to estimating prevalence—how common a disease or exposure is in a population at that time. However, because exposure and disease are assessed simultaneously, you can’t determine which came first, so incidence and temporality can’t be established. This distinguishes them from cohort studies, which follow people over time to observe new cases, and from experimental studies that assign exposures.