Bias from conditioning on live birth in pregnancy cohorts: an illustration based on neurodevelopment in children after prenatal exposure to organic pollutants
Bias from conditioning on live birth in pregnancy cohorts: an illustration based on neurodevelopment in children after prenatal exposure to organic pollutants
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DOI：
10.1093/ije/dyu249
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发表时间：
2015-02-01
影响因子：
7.7
通讯作者：
Arah, Onyebuchi A.
中科院分区：
文献类型：
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作者：
Liew, Zeyan;Olsen, Jorn;Arah, Onyebuchi A.
只有60-70%的受精卵可能会导致活产，而非常早期的胎儿丢失主要是被忽视的。只有活产婴儿才能确定的结果，对于那些活不到出生的婴儿来说，将是缺失的。在这篇文章中，我们说明了一个常见的偏见结构（导致“活产偏见”），产生于研究产前暴露于环境因素对长期健康结果之间的活产只有在怀孕队列。为了说明这一点，我们以学龄儿童产前暴露于全氟烷基物质（PFAS）和注意力缺陷多动障碍（ADHD）为例。PFAS是一种持久性有机污染物，可能影响人类生殖力，并对神经发育有毒。我们模拟了几个假设的情况下，从丹麦国家出生队列的特点，发现一个弱的逆关联可能会出现，即使PFAS不引起ADHD，但有相当大的影响胎儿存活。负偏倚的幅度通常很小，调整结局和胎儿丢失的常见原因可以减少偏倚。我们的例子强调了需要确定妊娠丢失的决定因素，以及在观察性研究中对活产条件产生的偏倚进行量化的重要性。
Only 60-70% of fertilized eggs may result in a live birth, and very early fetal loss mainly goes unnoticed. Outcomes that can only be ascertained in live-born children will be missing for those who do not survive till birth. In this article, we illustrate a common bias structure (leading to 'live-birth bias') that arises from studying the effects of prenatal exposure to environmental factors on long-term health outcomes among live births only in pregnancy cohorts. To illustrate this we used prenatal exposure to perfluoroalkyl substances (PFAS) and attention-deficit/hyperactivity disorder (ADHD) in school-aged children as an example. PFAS are persistent organic pollutants that may impact human fecundity and be toxic for neurodevelopment. We simulated several hypothetical scenarios based on characteristics from the Danish National Birth Cohort and found that a weak inverse association may appear even if PFAS do not cause ADHD but have a considerable effect on fetal survival. The magnitude of the negative bias was generally small, and adjusting for common causes of the outcome and fetal loss can reduce the bias. Our example highlights the need to identify the determinants of pregnancy loss and the importance of quantifying bias arising from conditioning on live birth in observational studies.