A cohort study finds that alcohol consumption is associated with liver cirrhosis (RR = 4.5). However, cigarette smoking, which is more common among heavy drinkers, is independently associated with liver cirrhosis. The apparent association between alcohol and cirrhosis is distorted by smoking. This is an example of:
- A Effect modification
- B Selection bias
- C Confounding ✓
- D Misclassification bias
Correct answer: C. Confounding
Explanation
Confounding occurs when a third variable (the confounder) is associated with both the exposure and the outcome, distorting the apparent exposure-outcome relationship. A confounder must meet three criteria: associated with exposure, associated with outcome independent of exposure, and not on the causal pathway. Effect modification refers to the situation where the effect of exposure varies across strata of another variable.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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