For a variable to act as a true confounder of an exposure-disease association, which set of conditions must be satisfied?
- A It must be associated with the exposure, be an independent risk factor for the disease, and not be an intermediate step in the causal chain ✓
- B It must be associated with the exposure, be an independent risk factor for the disease, and lie on the causal pathway between them
- C It must be caused by both the exposure and the disease, regardless of timing
- D It must be statistically associated with the disease in the crude analysis alone
Correct answer: A. It must be associated with the exposure, be an independent risk factor for the disease, and not be an intermediate step in the causal chain
Explanation
Three conditions define a confounder: association with the exposure in the source population, independent causal association with the outcome, and exclusion from the causal pathway between exposure and disease. If the variable lies on the causal pathway, adjusting for it removes part of the true effect, making it a mediator, not a confounder. Crude association with disease alone is insufficient.
Reference: Gordis Epidemiology, 6th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.