A researcher conducts a cohort study comparing smokers and non-smokers for lung cancer incidence over 20 years. Loss to follow-up occurs disproportionately among the sickest smokers who died early. This is best described as:
- A Healthy worker effect bias
- B Attrition bias resulting in underestimation of the true relative risk ✓
- C Neyman (prevalence-incidence) bias
- D Length-biased sampling
Correct answer: B. Attrition bias resulting in underestimation of the true relative risk
Explanation
When sicker participants (those more exposed and more diseased) are disproportionately lost to follow-up, the remaining smoker cohort appears healthier than the true smoking population. This differential attrition dilutes the exposure-disease association, causing underestimation of the relative risk — a form of attrition (loss-to-follow-up) bias. Healthy worker effect refers to employed workers being healthier than the general population. Neyman bias occurs in prevalence studies when fatal or rapidly cured cases are missed.
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.