"Assessing Mediation Effects for Survival Types of Outcomes"
April 21, 2009 @ 3:30 pm - 4:30 pm
Bin Huang, PhD, Children's Hosp.Med.Ctr., Cincinnati
Location: BRB - 251
TITLE: Assessing Mediation Effects for Survival Types of Outcomes
Assessing mediation effect helps elucidate causal pathway from an exposure to an outcome. For Survival types of outcomes, Lin et al (SIM, 1997) method is commonly used for assessing mediation effect. Their method defines the mediation effect following PE ratio based on two Cox models, which subject to model misspecification. The model misspecification issue was addressed by establishing conditions under which the method is valid. Recently, Ghosh (SIM 2007) proposed jointly modeling two AFT models, and estimating mediation effect semi-parametrically by a U statistics. It overcomes model misspecification, but is computational intensive and lack of flexibility to incorporate additional covariates. Here, the proposed new approach jointly modeling two Cox models, is able to overcome model misspecification problem, and is flexible and computationally feasible to incorporate additional covariates. Our simulation results are comparable to Lin's under their specified conditions, and show clear advantages in other settings. Case study will be conducted using ACTG019 data, evaluating mediation effect of CD4 count to the treatment effect of an HIV/AIDS clinical trial.