A1190
Title: Identification and estimation of mediational effects of longitudinal modified treatment policies
Authors: Ivan Diaz - NYU Langone Health (United States) [presenting]
Abstract: A comprehensive semiparametric approach is demonstrated to causal mediation analysis, addressing the complexities inherent in settings with longitudinal and continuous treatments, confounders, and mediators. The methodology utilizes a nonparametric structural equation model and a cross-fitted sequential regression technique based on doubly robust pseudo-outcomes, yielding an efficient, asymptotically normal estimator without relying on restrictive parametric modeling assumptions. The motivation is a recent scientific controversy regarding the effects of invasive mechanical ventilation (IMV) on the survival of COVID-19 patients, considering acute kidney injury (AKI) as a mediating factor. The possibility of "inconsistent mediation" is highlighted, in which the direct and indirect effects of the exposure operate in opposite directions. The significance of mediation analysis is discussed for scientific understanding and its potential utility in treatment decisions.
