National Center for Health Statistics, Centers for Disease Control and Prevention, Hyattsville, Maryland, USA.
Am J Epidemiol. 2011 Jan 1;173(1):1-9. doi: 10.1093/aje/kwq341. Epub 2010 Nov 8.
In studies of weight and mortality, the construct of reverse causation has come to be used to imply that the exposure-outcome relation is biased by weight loss due to preexisting illness. Observed weight-mortality associations are sometimes thought to result from this bias. Evidence for the occurrence of such bias is weak and inconsistent, suggesting that either the analytical methods used have been inadequate or else illness-related weight loss is not an important source of bias. Deleting participants has been the most frequent approach to control possible bias. As implemented, this can lead to deletion of almost 90% of all deaths in a sample and to deletion of more overweight and obese participants than participants with normal or below normal weight. Because it has not been demonstrated that the procedures used to adjust for reverse causation increase validity or have large or systematic effects on relative risks, it is premature to consider reverse causation as an important cause of bias. Further research would be useful to elucidate the potential effects and importance of reverse causation or illness-related weight loss as a source of bias in the observed associations between weight and mortality in cohort studies.
在体重与死亡率的研究中，反向因果关系的概念被用来暗示，由于预先存在的疾病导致的体重下降会使暴露-结果关系产生偏差。观察到的体重-死亡率关联有时被认为是这种偏差的结果。发生这种偏差的证据薄弱且不一致，这表明要么使用的分析方法不够充分，要么与疾病相关的体重减轻不是造成偏差的重要原因。删除参与者一直是控制可能偏差的最常见方法。实际上，这可能导致在样本中删除几乎 90%的所有死亡，并且删除的超重和肥胖参与者多于体重正常或低于正常的参与者。由于尚未证明用于调整反向因果关系的程序可以提高有效性，或者对相对风险有大的或系统的影响，因此将反向因果关系视为偏倚的一个重要原因还为时过早。进一步的研究将有助于阐明反向因果关系或与疾病相关的体重减轻作为队列研究中体重与死亡率之间观察到的关联中的偏倚来源的潜在影响和重要性。
