Which study design measures INCIDENCE (new cases of disease over time)?

Correct answer: D. Cohort study

• A. Cross-sectional studies measure PREVALENCE (disease burden at a single point in time) — they cannot measure incidence.
• B. Case-control studies start with disease status (cases vs. controls) and look backward for risk factors — they measure odds ratio, not true incidence.
• C. Systematic reviews synthesize existing evidence but do not directly measure incidence through primary data collection.
• D. Correct. Cohort studies follow a defined population over time and observe who develops the disease, directly measuring INCIDENCE (rate of new cases). Prospective cohorts are the most methodologically rigorous for measuring incidence.