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Variable Selection for Confounding Adjustment in High-dimensional Covariate Spaces When Analyzing Healthcare
Sebastian Schneeweiss1, Wesley Eddings, Robert J Glynn
1From the aDivision of Pharmacoepidemiology and Pharmacoeconomics, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA; and bAetion Inc., New York, NY.
Data-adaptive methods for confounding adjustment in electronic healthcare databases showed that standard variable selection performed well. Minor gains in accuracy were observed with Bayesian regression for rare outcomes.
Area of Science:
- Health Informatics
- Epidemiology
- Biostatistics
Background:
- Data-adaptive approaches to confounding adjustment offer advantages over expert knowledge for analyzing electronic healthcare databases.
- These methods are particularly useful for rapid analysis of multiple databases.
- Reliable empirical identification and adjustment of outcome predictors are key to improving analytical performance.
Purpose of the Study:
- To evaluate data-adaptive confounding adjustment strategies in electronic healthcare databases.
- To compare the performance of a base-case high-dimensional propensity score (hdPS) algorithm with augmented variable selection methods.
- To assess the impact of different variable selection and estimation techniques on treatment effect estimates.
Main Methods:
- A base-case high-dimensional propensity score (hdPS) algorithm was implemented across five cohort studies.
- Variable selection was augmented using alternative strategies, including adjusted outcome-confounder associations (RRCD) and joint modeling (Lasso, Bayesian regression).
- Propensity scores and outcome models were directly estimated using over 1,500 variables (Lasso, Bayesian regression, Ridge).
Main Results:
- Most tested augmentations to the base-case hdPS did not significantly alter estimates due to wide confidence intervals.
- Bayesian regression and Lasso for estimating RRCD minimally improved estimates in three of five studies.
- Direct outcome estimation using Lasso yielded the poorest performance.
Conclusions:
- The standard heuristic of variable reduction in hdPS adjustment performed comparably to alternative approaches across diverse settings.
- Bayesian outcome regression may offer slight improvements in variable selection for propensity score estimation with rare outcomes.
- The findings support the utility of data-adaptive methods while highlighting the robustness of basic hdPS variable selection strategies.
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