In a prospective cohort study examining the association between occupational silica dust exposure and lung fibrosis, workers who developed severe respiratory symptoms were more likely to leave their job and thus were lost to follow-up. This scenario best illustrates which type of bias?

• A Differential loss to follow-up (attrition bias) ✓
• B Healthy worker effect
• C Berkson's bias
• D Neyman (prevalence-incidence) bias

Explanation

When individuals with the outcome of interest (or worse disease) are disproportionately lost to follow-up, this is differential attrition bias. In this scenario workers who get sicker leave the industry, so the cohort becomes enriched with healthier survivors, underestimating the incidence of fibrosis. The healthy worker effect describes the baseline phenomenon that employed workers are healthier than the general population, not systematic dropout. Berkson's bias arises from hospital case-control selection. Neyman bias occurs when prevalent cases are studied instead of incident cases.

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

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Written and medically reviewed by the StethoPrep medical team.