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Confounding — USMLE Step 3 MCQ

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ModeratePreventive Medicine, Epidemiology, BiostatisticsConfoundingUSMLE Step 3

An observational study finds that coffee drinkers have higher rates of lung cancer. After adjustment for smoking, the association nearly disappears. The investigators conclude that the crude association was distorted by another factor related to both exposure and outcome. Which of the following is the most likely explanation for this patient's findings?

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Correct answer: E — Confounding

Smoking is associated with coffee drinking and lung cancer and distorts the exposure-outcome relationship, which is confounding.

Reference: Modern Epidemiology