An occupational health researcher compares mortality rates of factory workers with the general population and finds that workers have lower overall mortality despite hazardous exposures. This apparent protective effect is best explained by which phenomenon?
- A Healthy worker effect, a form of selection bias ✓
- B Hawthorne effect due to being observed
- C Recall bias in ascertainment of occupational history
- D Confounding by age differences between groups
Correct answer: A. Healthy worker effect, a form of selection bias
Explanation
Employed populations are systematically healthier than the general population because serious illness prevents employment, so comparing workers with everyone, including the chronically ill and unemployed, spuriously lowers worker mortality. This is the healthy worker effect, a classic selection bias in occupational cohort studies. The Hawthorne effect alters behavior under observation, and recall bias applies to retrospective exposure reporting, neither of which explains lower baseline mortality.
Reference: Park's Textbook of Preventive and Social Medicine, 26th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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