biostudies-literatureCui YTchetgen TchetgenNational University of Singapore and Singapore Ministry of EducationNIA NIH HHSNational Institutes of Health101-118https://www.ebi.ac.uk/biostudies/studies/S-EPMC9919489biostudies-literatureUnknown110(1)Robins (1998) introduced marginal structural models, a general class of counterfactual models for the joint effects of time-varying treatments in complex longitudinal studies subject to time-varying confounding. Robins (1998) established the identification of marginal structural model parameters under a sequential randomization assumption, which rules out unmeasured confounding of treatment assignment over time. The marginal structural Cox model is one of the most popular marginal structural models for evaluating the causal effect of time-varying treatments on a censored failure time outcome. In this paper, we establish sufficient conditions for identification of marginal structural Cox model parameters with the aid of a time-varying instrumental variable, in the case where sequential randBiometrikaInstrumental variable estimation of the marginal structural Cox model for time-varying treatments.PMC9919489R01 AG065276Cui YTchetgen Tchetgen EMichael HTanser FfalseInstrumental variable estimation of the marginal structural Cox model for time-varying treatments.Robins (1998) introduced marginal structural models, a general class of counterfactual models for the joint effects of time-varying treatments in complex longitudinal studies subject to time-varying confounding. Robins (1998) established the identification of marginal structural model parameters under a sequential randomization assumption, which rules out unmeasured confounding of treatment assignment over time. The marginal structural Cox model is one of the most popular marginal structural models for evaluating the causal effect of time-varying treatments on a censored failure time outcome. In this paper, we establish sufficient conditions for identification of marginal structural Cox model parameters with the aid of a time-varying instrumental variable, in the case where sequential rand2023-01-01T00:00:00Z2023 Mar2026-03-27T16:33:25.958Z2025-04-07T04:28:37.387ZS-EPMC99194893679884110.1093/biomet/asab062