Define concurrent cohort study.

• A. A cohort study where the study group assembled in present and followed in future
• B. A cohort study where past records are used to assemble the group and followed into the future
• C. A cross-sectional study used for quick snapshot
• D. A randomized trial with a control group

Answer: (A)

Concurrent cohort study means enrolling participants in the present and following them forward in time to observe outcomes, with exposure status established at the start. This prospective approach allows you to clear temporality between exposure and outcome and to calculate incidence and relative risk as events unfold. Using past records to assemble the group and then following into the future is a historical (retrospective) cohort, not concurrent. A cross-sectional study provides a single snapshot in time, not a forward-looking follow-up. A randomized trial assigns exposure by assignment, which is a different study design.