A Unified Approach for Estimation of a Treatment Effect When the Outcome Is Truncated by Death

• Activity Number: 456
• Type: Invited
• Date/Time: Wednesday, August 7, 2013 : 8:30 AM to 10:20 AM
• Sponsor: ENAR
• Author(s): Eric Tchetgen Tchetgen *+
• Companies: Harvard University
• Keywords: Causal inference, Truncation by death, Survivor Average Causal Effect, Double robustness

Abstract

In longitudinal studies, outcomes ascertained at follow-up are typically undefined for individuals who die prior to the follow-up visit. In such settings, outcomes are said to be truncated by death and inference about the effects of a point treatment or exposure, restricted to individuals alive at the follow-up visit, could be biased even if as in experimental studies, treatment assignment were randomized. To account for truncation by death, the survivor average causal effect (SACE), defines the effect of treatment on the outcome for the subset of individuals that would have survived regardless of exposure status. In this talk, the author nonparametrically identifies SACE by leveraging post-exposure longitudinal measurements that simultaneously mediate the effects of exposure on survival and on the outcome of interest. A novel simple weighted analysis involving a consistent estimate of the survival process, is shown to produce consistent estimates of SACE. The approach is illustrated and compared to existing analytic methods in an application concerning the effects of smoking on cognitive decline in an aging population subject to truncation by death.