Miettinen O S
Scand J Work Environ Health. 1982 Sep;8(3):159-68. doi: 10.5271/sjweh.2479.
"Synergism" of two factors in the causation or prevention of an all-or-none event means the existence of instances in which both factors are needed for the effect, while "antagonism" means that at least one can block the solo effect of the other. The manifestation of such interdependences--or of their complement, independence--in terms of event rates is complicated by the correlation of the susceptibilities to the two factors. Thus, given the risk difference (RD) values representing the solo effects, the RD corresponding to the joint exposure has a range consistent with independence so that independence cannot be inferred even from very ample data without knowledge of the degree of correlatedness of the susceptibilities. The definition of this range is closely analogous for causal and preventive factors, respectively. However, when knowledge about interdependence is used in inference about the factors' interrelation in the mechanisms for the effect, sharp distinctions may have to be made between causal and preventive factors. In each case, the interdependence is a result of the interrelation of the actions of the two factors and/or interaction between them. Operational decisions, having to do with the wisdom of the joint exposure, can be guided by knowledge about the interdependence of the factors; however, knowledge of the risks corresponding to the various exposures is a sufficient guide, without any need for inferences about causal or preventive interdependence.
在全或无事件的因果关系或预防中，两个因素的“协同作用”意味着存在这样的情况，即两种因素对结果都是必需的，而“拮抗作用”则意味着至少有一种因素可以阻断另一种因素的单独作用。这些相互依存关系——或者它们的补充，独立性——在事件发生率方面的表现，由于对这两种因素的易感性之间的相关性而变得复杂。因此，给定代表单独作用的风险差异（RD）值，对应于联合暴露的RD有一个与独立性一致的范围，所以即使从非常丰富的数据中，如果不知道易感性的相关程度，也无法推断出独立性。对于因果因素和预防因素，这个范围的定义分别非常相似。然而，当关于相互依存关系的知识被用于推断因素在效应机制中的相互关系时，可能必须在因果因素和预防因素之间做出明确区分。在每种情况下，相互依存关系都是两种因素的作用相互关联和/或它们之间相互作用的结果。与联合暴露的合理性相关的操作决策，可以由关于因素相互依存关系的知识来指导；然而，关于各种暴露对应的风险的知识就是一个充分的指导，无需对因果或预防相互依存关系进行推断。
