To avoid confounding in a cohort study, what practice is recommended?

• A. Exclude Patients With Conditions That Independently Affect Outcome
• B. Include All Patients
• C. Randomly Assign Exposure
• D. Collect More Data

Answer: (A)

Confounding occurs when a factor influences both the exposure and the outcome, muddying the true relationship. In a cohort study, restricting the study population by excluding individuals who have conditions that could independently affect the outcome directly removes that potential confounding path, making the exposure–outcome association clearer. Including all patients leaves those confounding conditions in place; randomizing exposure isn’t typically feasible in a cohort study and is more the domain of randomized trials; collecting more data alone doesn’t guarantee control for confounding unless the analysis specifically adjusts for it. Note that restricting improves internal validity but can limit generalizability.