Dealing with Time-Varying Eligibility for Exposure Using the Target Trials Approach to Causal Inference
Improper handling of time-dependent exposures can result in ill-defined causal effects, residual time-dependent confounding, and immortal time bias. Marginal structural models were proposed for time-varying exposures where confounders may be affected by prior treatment. However, typical definitions of exposure effects no longer apply when eligibility for exposure varies over time. We demonstrate how “treatment strategies” in the context of a target trial (Hernán and Robins, 2016) provide a solution using two real examples. The first example involves post-baseline contraindications to Direct Oral Anticoagulants (DOACs) in a study that aims to contrast DOACs with warfarin in patients with atrial fibrillation. The second involves contrasting trimester-specific exposures during pregnancy when some women deliver in the second trimester. For both of these examples, we define effects based on "treatment strategies" and describe alternate implementations of existing causal inference methods.
Date and Time
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Language of Oral Presentation
English
Language of Visual Aids
English