A mortality study of workers in a pesticide manufacturing plant reports a standardized mortality ratio of 0.72 for all-cause death when compared with the general population of the region. Investigators suspect this underestimate of occupational harm. What is the most likely explanation?
- A Recall bias inflating exposure ascertainment among survivors
- B Lead time bias introduced by earlier detection of deaths in workers
- C The healthy worker effect, since employed populations are systematically healthier than the general population ✓
- D Overmatching of workers to the regional population
Correct answer: C. The healthy worker effect, since employed populations are systematically healthier than the general population
Explanation
Industrial employment requires reasonable baseline health, and those who fall seriously ill often leave work, so workers carry lower background mortality than the general population, which includes the chronically ill and unemployed. Comparing worker mortality against this healthier-than-average reference makes the SMR spuriously low. The standard remedy is comparison with an external occupational cohort or internal unexposed workers rather than the general population.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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