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Efficient risk set sampling when a time-dependent exposure is present: matching for time to exposure versus exposure
Martin Wolkewitz1, J Beyersmann, P Gastmeier
1Institute of Medical Biometry and Medical Informatics, University Medical Center Freiburg, 79104 Freiburg, Germany. wolke@fdm.uni-freiburg.de
Methods of Information in Medicine
|August 7, 2009
Summary
Matching for time-dependent exposures can introduce bias, especially with frequent exposures. Exposure density sampling offers an unbiased alternative for analyzing time-dependent exposures in subcohort studies.
Area of Science:
- Epidemiology
- Biostatistics
- Health Research Methods
Background:
- Time-dependent exposures can bias study results if not properly analyzed.
- Matching for time to exposure is a common method to account for time-dependency but may still introduce bias.
- Subcohort sampling can save resources but requires careful consideration of potential biases.
Purpose of the Study:
- To assess the extent of bias introduced by matching for time to exposure.
- To introduce and evaluate exposure density sampling as an alternative method.
Main Methods:
- Comparison of matching for time to exposure and exposure density sampling against a correct analysis method.
- Evaluation using both real-world data from the SIR-3 study and a simulation study.
Main Results:
- Matching for time to exposure reduces but does not eliminate time-dependent bias.
- The bias from matching decreases with less frequent exposures.
- Exposure density sampling provided unbiased results in simulations.
Conclusions:
- Matching for time to exposure is acceptable only for rare exposures.
- Exposure density sampling is recommended when subcohorts are necessary to save resources.
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