Fulcher Isabel R, Shpitser Ilya, Marealle Stella, Tchetgen Tchetgen Eric J
Harvard T.H. Chan School of Public Health, Boston, USA.
Johns Hopkins University, Baltimore, USA.
J R Stat Soc Series B Stat Methodol. 2020 Feb;82(1):199-214. doi: 10.1111/rssb.12345. Epub 2019 Nov 8.
Standard methods for inference about direct and indirect effects require stringent no-unmeasured-confounding assumptions which often fail to hold in practice, particularly in observational studies. The goal of the paper is to introduce a new form of indirect effect, the population intervention indirect effect, that can be non-parametrically identified in the presence of an unmeasured common cause of exposure and outcome. This new type of indirect effect captures the extent to which the effect of exposure is mediated by an intermediate variable under an intervention that holds the component of exposure directly influencing the outcome at its observed value. The population intervention indirect effect is in fact the indirect component of the population intervention effect, introduced by Hubbard and Van der Laan. Interestingly, our identification criterion generalizes Judea Pearl's front door criterion as it does not require no direct effect of exposure not mediated by the intermediate variable. For inference, we develop both parametric and semiparametric methods, including a novel doubly robust semiparametric locally efficient estimator, that perform very well in simulation studies. Finally, the methods proposed are used to measure the effectiveness of monetary saving recommendations among women enrolled in a maternal health programme in Tanzania.
用于推断直接效应和间接效应的标准方法需要严格的无未测量混杂假设，而这些假设在实际中往往不成立，尤其是在观察性研究中。本文的目的是引入一种新的间接效应形式，即总体干预间接效应，它在存在暴露和结局的未测量共同原因的情况下可以进行非参数识别。这种新型间接效应捕捉了在一种干预下，暴露效应由中间变量介导的程度，该干预将暴露直接影响结局的部分保持在其观察值。总体干预间接效应实际上是由哈伯德和范德·拉恩提出的总体干预效应的间接组成部分。有趣的是，我们的识别标准推广了朱迪亚·珀尔的前门标准，因为它不要求未由中间变量介导的暴露无直接效应。为了进行推断，我们开发了参数和半参数方法，包括一种新颖的双稳健半参数局部有效估计器，这些方法在模拟研究中表现良好。最后，所提出的方法用于衡量坦桑尼亚一项孕产妇健康计划中登记的妇女的货币储蓄建议的有效性。
