Which study design BEST measures risk factors and their association with disease over time?

Correct answer: C. Longitudinal (prospective cohort) study

• A. Incorrect. Case-control studies are retrospective — they look back from the outcome and are susceptible to recall bias.
• B. Incorrect. Case reports describe single patients — no comparative data.
• C. Correct. LONGITUDINAL (prospective cohort) studies follow subjects over TIME, measuring exposures and tracking disease development. They are ideal for measuring RISK and ASSOCIATIONS because they establish temporal sequence (cause precedes effect).
• D. Incorrect. Cross-sectional studies measure prevalence at one point — cannot establish temporal relationships.