In a prospective cohort study on diet and colorectal cancer, participants who join the study tend to be health-conscious, physically active, and have lower cancer risk than the general population. This causes:
- A Healthy worker effect — a type of selection bias ✓
- B Information bias from dietary recall error
- C Berkson's bias due to hospitalization
- D Confounding by socioeconomic status
Correct answer: A. Healthy worker effect — a type of selection bias
Explanation
The healthy worker effect (or healthy volunteer effect in population-based cohorts) is a type of selection bias where study participants are healthier than the general population, typically leading to an underestimate of disease risk. In occupational cohort studies, employed workers are healthier than the unemployed general population used as reference, artificially lowering observed risk. This also applies to volunteer cohorts where participants tend to be health-conscious.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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