Primary Submission Category: Mediation
Identification and estimation of mediational effects of longitudinal modified treatment policies
Authors: Brian Gilbert, Katherine Hoffman, Nicholas Williams, Kara Rudolph, Iván Díaz, Edward Schenck,
Presenting Author: Brian Gilbert*
We put forward a comprehensive semiparametric approach to causal mediation analysis, addressing the complexities inherent in settings with longitudinal and continuous treatments. Our methodology utilizes a nonparametric structural equation model and a sequential regression technique, yielding an efficient estimator without relying on restrictive modeling assumptions. We are motivated by a recent scientific controversy regarding the effects of invasive mechanical ventilation (IMV) on the survival of COVID-19 patients in the ICU, considering acute kidney injury (AKI) as a mediating factor. We highlight the possibility of “inconsistent mediation,” in which the direct and indirect effects of the exposure operate in opposite directions. We discuss the significance of mediation analysis for scientific understanding and its potential utility in treatment decisions.