A cohort study finds mortality from cardiovascular disease among factory employees to be substantially lower than in the surrounding community, even though the workplace involves known cardiac stressors. Before concluding the job is protective, the investigator should consider:
- A Interviewer bias
- B Information bias from surrogate respondents
- C Healthy worker effect ✓
- D Confounding by diet
Correct answer: C. Healthy worker effect
Explanation
The healthy worker effect is a form of selection bias in occupational cohorts: workers must be comparatively fit to obtain and retain employment, so their mortality is systematically lower than the general population, which includes the ill, disabled and institutionalised. Comparisons should ideally use an external workforce or internal comparison groups. Interviewer bias and surrogate information affect data quality, not baseline group selection.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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