Conditioning on intermediates in perinatal epidemiology.
Conditioning on intermediates in perinatal epidemiology.
复制标题
围产期流行病学中间体的调理。
DOI：
10.1097/ede.0b013e31823aca5d
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发表时间：
2012-01
期刊：
影响因子：
--
通讯作者：
Schisterman EF
中科院分区：
文献类型：
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作者：
VanderWeele TJ;Mumford SL;Schisterman EF
在围产期流行病学中，通常的做法是计算暴露与围产期结局之间的妊娠年龄特异性或出生体重特异性相关性。例如，生育年龄或出生体重可能位于从暴露到结果的路径上。由于各种原因，这种以潜在中间体为条件的做法受到了批评。首先，如果人们对评估暴露对结果的总体影响感兴趣，则没有必要对中间体进行分层，实际上不分层很重要。第二，如果人们确实以一个中间体为条件，试图获得可能被认为是暴露对结果的“直接影响”，那么就会出现各种偏见和矛盾的结果。现在理论和经验上都有很好的证明，当中间和结果有一个不可测量的共同原因时，为中间调整的关联会受到偏见的影响。在本文中，我们提出了三种方法，以促进有效的推理时，有条件的中间效果。这三种方法分别对应于（i）以中间体的预测风险为条件，（ii）以中间体本身为条件，结合敏感性分析，以及（iii）以无论接受何种暴露都会发生中间体的个体亚组为条件。第二种和第三种方法都需要进行敏感性分析，并得出一系列估计值。这三种方法中的每一种都可以用来解决“出生体重悖论”，即母亲吸烟等暴露似乎对低出生体重婴儿具有保护作用。本文所述的各种方法学方法适用于围产期流行病学的一些类似的设置。
It is common practice in perinatal epidemiology to calculate gestational-age-specific or birth-weight-specific associations between an exposure and a perinatal outcome. Gestational age or birth weight, for example, might lie on a pathway from the exposure to the outcome. This practice of conditioning on a potential intermediate has come under critique for various reasons. First, if one is interested in assessing the overall effect of an exposure on an outcome, it is not necessary to stratify, and indeed it is important not to stratify, on an intermediate. Second, if one does condition on an intermediate, to try to obtain what might conceived of as a “direct effect” of the exposure on the outcome, then various biases and paradoxical results can arise. It is now well documented theoretically and empirically, that when there is an unmeasured common cause of the intermediate and the outcome, associations adjusted for the intermediate are subject to bias. In this paper we propose three approaches to facilitate valid inference when effects conditional on an intermediate are in view. These three approaches correspond to (i) conditioning on the predicted risk of the intermediate, (ii) conditioning on the intermediate itself in conjunction with sensitivity analysis, and (iii) conditioning on the subgroup of individuals for whom the intermediate would occur irrespective of the exposure received. The second and third approaches both require sensitivity analysis, and they result in a range of estimates. Each of the three approaches can be used to resolve the “birth-weight paradox” that exposures such as maternal smoking appear to have a protective effect among low-birth-weight infants. The various methodologic approaches described in this paper are applicable to a number of similar settings in perinatal epidemiology.