A case-control study examining smoking and bladder cancer matches every case and control on daily coffee intake, a habit strongly correlated with smoking in the study population. The most likely consequence of this matching strategy is:
- A Reduced ability to detect a genuine association between the exposure and disease ✓
- B Selection bias due to unequal recruitment of cases and controls
- C An inflated odds ratio caused by induced confounding
- D Information bias from inconsistent exposure measurement
Correct answer: A. Reduced ability to detect a genuine association between the exposure and disease
Explanation
Matching on a variable closely tied to the exposure of interest constitutes overmatching. By forcing cases and controls to have similar coffee intake, the design strips away much of the variability that distinguishes smokers from non-smokers, driving the measured odds ratio toward the null and wasting statistical efficiency. Coffee is not a strong independent confounder here, so the cost of matching outweighs any benefit. This remains a recognized pitfall of individual matching in case-control designs.
Reference: Gordis Epidemiology, 6th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.