Department of Epidemiology, CAPHRI School for Public Health and Primary Care, Maastricht University Medical Centre, Peter Debyeplein 1, 6229 HA Maastricht, The Netherlands.
J Clin Epidemiol. 2013 Feb;66(2):192-6. doi: 10.1016/j.jclinepi.2012.06.023.
Studies of determinants of recurrent disease often give unexpected results. In particular, well-established risk factors may seem not to have much influence on the recurrence risk. Recently, it has been argued that such paradoxical findings may be because of the bias caused by the selection of patients based on the occurrence of an earlier episode of the disease. This bias was referred to as index event bias. Here, we give a theoretical quantitative example of index event bias, showing that, as a result of selection of patients on the basis of previous disease: (1) risk factors become inversely associated when they are not in the unselected population, and (2) the crude association between the risk factor of interest and disease becomes biased toward the null.
复发疾病的决定因素研究常常会得出出人意料的结果。特别是，一些公认的危险因素似乎对复发风险的影响不大。最近，有人认为，之所以会出现这种矛盾的结果，可能是由于根据疾病的早期发作来选择患者而导致的偏倚。这种偏倚被称为指示事件偏倚。在这里，我们给出了一个指示事件偏倚的理论定量实例，表明由于基于先前疾病选择了患者：（1）当危险因素在未选择人群中不相关时，它们之间的关联会呈现出相反的趋势；（2）感兴趣的危险因素与疾病之间的原始关联会偏向于无效。
