A researcher studying the association between alcohol consumption and oropharyngeal cancer notices that smokers tend to drink more alcohol. When controlling for smoking, the association between alcohol and cancer weakens substantially. This phenomenon is BEST described as:
- A Confounding by smoking ✓
- B Effect modification (interaction)
- C Information bias
- D Berkson's bias
Explanation
Confounding occurs when a third variable (confounder) is associated with both the exposure and the outcome and distorts the observed exposure–outcome relationship. Smoking qualifies as a confounder here: it is associated with alcohol consumption (exposure) and independently causes oropharyngeal cancer (outcome). When controlling for it removes the association, this confirms confounding. Effect modification would be present if the alcohol–cancer association differed across strata of smoking; information bias relates to measurement error; Berkson's bias is a selection bias in hospital-based studies.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
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Written and medically reviewed by the StethoPrep medical team.