Which statement best describes cohort studies in terms of exposure manipulation?

• A. They randomize exposure to participants
• B. They manipulate exposure levels
• C. They observe exposure and outcomes without manipulating exposure
• D. They only assess exposures at a single time point

Answer: (C)

Cohort studies are observational, meaning researchers do not assign or change who is exposed. They start with groups defined by their real-life exposure status and then follow these groups over time to see who develops the outcome. There’s no randomization or deliberate manipulation of exposure by the investigators, which distinguishes them from experimental designs. If exposure were manipulated or randomized, that would be an interventional study rather than a cohort study. So, the key idea is that exposure and outcomes are observed as they occur, without manipulating exposure.