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- Title
Point: Risk Ratio Equations for Natural Direct and Indirect Effects in Causal Mediation Analysis of a Binary Mediator and a Binary Outcome—A Fresh Look at the Formulas.
- Authors
Samoilenko, Mariia; Lefebvre, Geneviève
- Abstract
In this article, we review the formulas for the natural direct and indirect effects' risk ratios introduced by Ananth and VanderWeele (Am J Epidemiol. 2011;174(1):99–108) for causal mediation analysis of a binary mediator and a binary outcome. In particular, we show that the closed-form equations Ananth and VanderWeele provided do not correspond to the log-binomial model specified by these authors for the mediator variable, but rather to a logistic model. We then provide risk ratio equations for natural direct and indirect effects that truly pertain to a log-binomial model. We conclude with a discussion on the practical implications of the binary mediator model's specification by analysts. The related impact can be negligible or not, depending on the rareness of the mediator.
- Subjects
PERINATAL death; DOSE-response relationship in biochemistry; PREMATURE infants; LOGISTIC regression analysis; RELATIVE medical risk; STATISTICAL models; ABRUPTIO placentae; ODDS ratio
- Publication
American Journal of Epidemiology, 2019, Vol 188, Issue 7, p1201
- ISSN
0002-9262
- Publication type
Article
- DOI
10.1093/aje/kwy275