Causal mediation analysis on failure time outcome without sequential ignorability

Cheng Zheng, Xiao Hua Zhou

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


Mediation analysis is an important topic as it helps researchers to understand why an intervention works. Most previous mediation analyses define effects in the mean scale and require a binary or continuous outcome. Recently, possible ways to define direct and indirect effects for causal mediation analysis with survival outcome were proposed. However, these methods mainly rely on the assumption of sequential ignorability, which implies no unmeasured confounding. To handle the potential confounding between the mediator and the outcome, in this article, we proposed a structural additive hazard model for mediation analysis with failure time outcome and derived estimators for controlled direct effects and controlled mediator effects. Our methods allow time-varying effects. Simulations showed that our proposed estimator is consistent in the presence of unmeasured confounding while the traditional additive hazard regression ignoring unmeasured confounding produces biased results. We applied our method to the Women’s Health Initiative data to study whether the dietary intervention affects breast cancer risk through changing body weight.

Original languageEnglish (US)
Pages (from-to)533-559
Number of pages27
JournalLifetime Data Analysis
Issue number4
StatePublished - Oct 1 2017
Externally publishedYes


  • Additive hazard model
  • Causal inference
  • Generalized estimating equation
  • Inverse censoring probability weighting

ASJC Scopus subject areas

  • Applied Mathematics

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