In the context of causal mediation analysis, prevailing notions of direct and indirect effects are based on nested counterfactuals. These can be problematic regarding interpretation and identifiability especially when the mediator is a time-dependent process and the outcome is survival or, more generally, a time-to-event outcome. We propose and discuss an alternative definition of mediated effects that does not suffer from these problems, and is more transparent than the current alternatives. Our proposal is based on the extended graphical approach of Robins and Richardson (in: Shrout (ed) Causality and psychopathology: finding the determinants of disorders and their cures, Oxford University Press, Oxford, 2011), where treatment is decomposed into different components, or aspects, along different causal paths corresponding to real world mechanisms. This is an interesting alternative motivation for any causal mediation setting, but especially for survival outcomes. We give assumptions allowing identifiability of such alternative mediated effects leading to the familiar mediation g-formula (Robins in Math Model 7:1393, 1986); this implies that a number of available methods of estimation can be applied.

中文翻译：

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用纵向介质定义因果关系和生存结果。

在因果中介分析的背景下，直接和间接影响的流行概念是基于嵌套的反事实。这些在解释和可识别性方面可能会出现问题，尤其是当调解员是一个与时间有关的过程，而结局是生存或更普遍的是事件发生后的结局时。我们提出并讨论了介导效应的替代定义，该定义不受这些问题的困扰，并且比当前替代方案更透明。我们的建议基于罗宾斯和理查森（Robins and Richardson）的扩展图形方法（见Shrout（ed）因果关系和精神病理学：发现疾病及其治愈的决定因素，牛津大学出版社，牛津，2011年），其中将治疗分解为不同的组成部分，或方面，沿着与现实世界机制相对应的不同因果路径。任何因果调解设置，尤其是对于生存结果。我们给出的假设允许对导致熟悉的中介g公式的此类替代介导效应进行可识别性（Robins in Math Model 7：1393，1986）；这意味着可以应用许多可用的估计方法。