Which study design most clearly provides a temporal (time) relationship between exposure and disease?

Correct answer: A. Cohort study

• A. Correct. Cohort studies follow subjects FORWARD in time from exposure to outcome, establishing temporal sequence (exposure precedes disease). Gold standard for demonstrating temporality in observational research.
• B. Incorrect. Case-control studies look BACKWARD from disease to exposure (retrospective) — temporal sequence is harder to establish.
• C. Incorrect. Cross-sectional studies measure exposure and disease simultaneously — no temporal sequence can be established.
• D. Incorrect. RCTs best establish causality, but cohort studies are the observational design most specifically demonstrating temporal relationships.