A study finds that the association between coffee drinking and myocardial infarction disappears after stratifying by smoking status. This phenomenon is best described as:

• A Effect modification by smoking
• B Interaction between coffee and smoking
• C Bias due to misclassification
• D Confounding by smoking ✓

Explanation

When a spurious or inflated association disappears after adjusting for a third variable, that variable is a confounder. A confounder must be associated with both exposure and outcome and not be in the causal pathway. In contrast, effect modification (interaction) means the effect of exposure differs by level of the modifier, and the association does not disappear but changes in magnitude or direction.

Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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