A cohort study compares mortality among factory employees with that of the general population and finds significantly lower death rates in the workers. The epidemiologist suspects this reflects the fact that employment requires a minimum level of health. This phenomenon is called:

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

Explanation

The healthy worker effect is a form of selection bias seen in occupational cohorts: workers must be reasonably fit to obtain and keep employment, so comparing them with the general population, which includes the chronically ill and disabled, spuriously lowers worker mortality. It biases the measured risk toward the null or below it. The remedy is comparison with an internal unexposed worker group rather than external population rates.

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.