Which type of study assesses both disease and exposure at the same time?

The correct answer is cross-sectional studies. These studies are unique in that they assess both disease status and exposure status simultaneously, providing a snapshot of the situation at a particular point in time. This type of study can help researchers identify associations between exposures and outcomes, but it does not establish causality due to the simultaneous measurement.

In contrast, prospective cohort studies follow a group over time to see how exposure affects the incidence of disease, while retrospective cohort studies look back in time to analyze exposures related to outcomes that have already occurred. Case-control studies, on the other hand, start with the outcomes and look back to determine exposure history. Each of these other study types has a different timeframe and methodology than cross-sectional studies, making them distinct in their purpose and outcomes.