An occupational cohort of factory workers shows lower all-cause mortality than the general population of the same region. An investigator concludes that the factory job protects against death. The most likely explanation for this spurious finding is:

• A Recall bias
• B Neyman's bias
• C Healthy worker effect ✓
• D Hawthorne effect

Explanation

Employed populations are systematically healthier than the general population because seriously ill and disabled individuals are excluded from employment. Comparing worker mortality with general population mortality therefore underestimates or even reverses true occupational risks. Recall bias applies to exposure ascertainment in case-control studies, Neyman's bias to prevalent-case selection, and Hawthorne effect to behaviour change under observation, none of which explains lower baseline mortality in workers.

Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.