Core features of cohort studies include which combination?

• A. Observational; longitudinal; analytic
• B. Experimental; cross-sectional; descriptive
• C. Qualitative; retrospective; exploratory
• D. Systematic reviews; meta-analysis; synthesis

Answer: (A)

Cohort studies are defined by watching a group of people over time to see how a exposure relates to later outcomes. They are observational because researchers don’t assign or manipulate who is exposed. They are longitudinal because data are collected across different time points, following participants as events unfold. They are analytic because the goal is to quantify associations—estimating risks or relative risks, and testing whether exposure affects the outcome.

That combination—observational, longitudinal, and analytic—best fits cohort design. It’s not experimental, since there’s no deliberate assignment of exposure. It’s not cross-sectional, which captures data at one moment rather than over time. It’s not purely descriptive, because cohort studies aim to analyze the relationship between exposure and outcome and produce measures of association. Systematic reviews or meta-analyses synthesize existing studies rather than generate new cohort data, and qualitative or exploratory approaches don’t focus on incidence or risk measures.