Chi Wang, Department of Biostatistics, College of Public Health, Biostatistics and Bioinformatics Shared Resource Facility, Markey Cancer Center, University of Kentucky

"Estimation of the Average Causal Effect while Accounting for Uncertainty in Confounder and Effect Modifier Selection"

Confounder selection and adjustment are essential elements of assessing the causal effect of an exposure or treatment in observational studies. We propose and evaluate a Bayesian method to estimate average causal effects in studies with a large number of potential confounders, relatively few observations, likely interactions between confounders and the exposure of interest, and uncertainty on which confounders and interaction terms should be included. Our method is applicable across all exposures and outcomes that can be handled through generalized linear models. In this general setting, estimation of the average causal effect is different from estimation of the exposure coefficient in the outcome model due to non-collapsibility. We implement a Bayesian bootstrap procedure to integrate over the distribution of potential confounders and to estimate the causal effect. Our method permits estimation of both the overall population causal effect and effects in specified subpopulations, providing clear characterization of heterogeneous exposure effects that may vary considerably across different covariate profiles. Applications of the method are demonstrated using the US Medicare brain tumor data and the Genetic Analysis Workshop 19 (GAW19) sequencing data.

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