Fairmont Queen Elizabeth (Montreal), December 7 - 10, 2012
In this study, we propose a flexible marginal structural Cox model with weighted cumulative exposure modeling (WCE MSM), which combines the Cox MSM and WCE approaches, thereby simultaneously addressing the two aforementioned analytical challenges. Specifically, by controlling for confounders using the inverse-probability-of-treatment weights and estimating the WCE with cubic regression splines, the new WCE MSM can estimate the total causal treatment effect, that accounts for both direct cumulative effects of past treatments and their `indirect effects', mediated by the TD mediators.
Simulation results confirm that the proposed WCE MSM yields accurate estimates of the causal treatment effect under settings of complex exposure effects and time-varying confounding. The new method was applied to the Swiss HIV Cohort Study data to reassess the association between antiretroviral treatment abacavir (ABC) and cardiovascular risk.