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Selection bias in population-based cancer case-control studies due to incomplete sampling frame coverage
Matthew C Walsh1, Amy Trentham-Dietz, Ronald E Gangnon
1University of Wisconsin-Madison, Middleton, WI 53562, USA. walsh2@wisc.edu
Summary
Many individuals opt out of health studies due to privacy, creating potential bias. This study shows differential opt-out rates in breast cancer cases, highlighting the need for ongoing bias assessment in case-control studies.
Area of Science:
- Epidemiology
- Biostatistics
- Public Health
Background:
- Growing privacy concerns lead individuals to opt out of population-based sampling frames.
- This trend poses challenges for selecting controls in case-control studies, potentially introducing bias if opt-out is linked to risk factors.
Purpose of the Study:
- To assess potential selection bias in case-control studies arising from differential opt-out rates in sampling frames.
- To evaluate the utility of selection probability ratios (SPRs) in predicting bias.
Main Methods:
- Linked breast cancer cases (N=2,988) from the Wisconsin women's health study (2004-2008) with a Wisconsin Department of Transportation (WDOT) driver's license master list.
- Calculated multivariate-adjusted selection probability ratios (SPRs) to estimate bias in a driver's license sampling frame.
Main Results:
- 32% of cases opted out of the WDOT sampling frame.
- Younger age (<40), higher income (>$50,000), lower parity, and hormone use were associated with significantly lower WDOT sampling frame coverage.
Conclusions:
- Differential opt-out among demographic and behavioral subgroups indicates potential for selection bias in case-control studies.
- SPRs are valuable tools for predicting bias direction when cases and controls originate from different sampling frames.
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