Journal
AMERICAN JOURNAL OF EPIDEMIOLOGY
Volume 191, Issue 6, Pages 1140-1151Publisher
OXFORD UNIV PRESS INC
DOI: 10.1093/aje/kwac043
Keywords
inverse probability of treatment weighting; overlap weighting; propensity score; survival function; trimming
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Funding
- Patient-Centered Outcomes Research Institute (PCORI), Washington, DC [ME-2018C2-13289]
- Agency for Healthcare Research and Quality [RFA-HS-14-006]
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This article introduces estimators that combine propensity score weighting and inverse probability of treatment weighting to estimate counterfactual survival functions. Simulation results demonstrate that overlap weighting consistently outperforms IPTW and trimming methods for time-to-event outcomes.
The inverse probability of treatment weighting (IPTW) approach is popular for evaluating causal effects in observational studies, but extreme propensity scores could bias the estimator and induce excessive variance. Recently, the overlap weighting approach has been proposed to alleviate this problem, which smoothly down-weights the subjects with extreme propensity scores. Although advantages of overlap weighting have been extensively demonstrated in literature with continuous and binary outcomes, research on its performance with time-to-event or survival outcomes is limited. In this article, we propose estimators that combine propensity score weighting and inverse probability of censoring weighting to estimate the counterfactual survival functions. These estimators are applicable to the general class of balancing weights, which includes IPTW, trimming, and overlap weighting as special cases. We conduct simulations to examine the empirical performance of these estimators with different propensity score weighting schemes in terms of bias, variance, and 95% confidence interval coverage, under various degrees of covariate overlap between treatment groups and censoring rates. We demonstrate that overlap weighting consistently outperforms IPTW and associated trimming methods in bias, variance, and coverage for time-to-event outcomes, and the advantages increase as the degree of covariate overlap between the treatment groups decreases.
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