The effect of a constraint on the maximum number of controls matched to each treated subject on the performance of full matching on the propensity score when estimating risk differences.

Content Provider	Europe PMC
Author	Austin, Peter C. Stuart, Elizabeth A.
Abstract	Many observational studies estimate causal effects using methods based on matching on the propensity score. Full matching on the propensity score is an effective and flexible method for utilizing all available data and for creating well‐balanced treatment and control groups. An important component of the full matching algorithm is the decision about whether to impose a restriction on the maximum ratio of controls matched to each treated subject. Despite the possible effect of this restriction on subsequent inferences, this issue has not been examined. We used a series of Monte Carlo simulations to evaluate the effect of imposing a restriction on the maximum ratio of controls matched to each treated subject when estimating risk differences. We considered full matching both with and without a caliper restriction. When using full matching with a caliper restriction, the imposition of a subsequent constraint on the maximum ratio of the number of controls matched to each treated subject had no effect on the quality of inferences. However, when using full matching without a caliper restriction, the imposition of a constraint on the maximum ratio of the number of controls matched to each treated subject tended to result in an increase in bias in the estimated risk difference. However, this increase in bias tended to be accompanied by a corresponding decrease in the sampling variability of the estimated risk difference. We illustrate the consequences of these restrictions using observational data to estimate the effect of medication prescribing on survival following hospitalization for a heart attack.
Related Links	https://europepmc.org/backend/ptpmcrender.fcgi?accid=PMC7821239&blobtype=pdf
Page Count	18
ISSN	02776715
Journal	Statistics in Medicine [Stat Med]
Volume Number	40
DOI	10.1002/sim.8764
PubMed Central reference number	PMC7821239
Issue Number	1
PubMed reference number	33027845
e-ISSN	10970258
Language	English
Publisher	John Wiley & Sons, Inc.
Publisher Date	2020-10-07
Publisher Place	Hoboken, USA
Access Restriction	Open
Rights License	This is an open access article under the terms of the http://creativecommons.org/licenses/by-nc-nd/4.0/ License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non‐commercial and no modifications or adaptations are made. © 2020 The Authors. Statistics in Medicine published by John Wiley & Sons Ltd.
Subject Keyword	full matching matching Monte Carlo simulations observational studies propensity score
Content Type	Text
Resource Type	Article
Subject	Statistics and Probability Epidemiology