Background The sibling comparison analysis is used to deal with unmeasured confounding. It has previously been shown that in the presence of non-shared unmeasured confounding, the sibling comparison analysis may introduce substantial bias depending on the sharedness of the unmeasured confounder and the sharedness of the exposure. We aimed to improve the awareness of this challenge of the sibling comparison analysis. Methods First, we simulated sibling pairs with an exposure, a confounder and an outcome. We simulated sibling pairs with no effect of the exposure on the outcome and with positive confounding. For varying degrees of sharedness of the confounder and the exposure and for varying prevalence of the exposure, we calculated the sibling comparison odds ratio (OR). Second, we provided measures for sharedness of selected treatments based on Danish health data. Results The confounded sibling comparison OR was visualized for varying degrees of sharedness of the confounder and the exposure and for varying prevalence of the exposure. The confounded sibling comparison OR was seen to increase with increasing sharedness of the exposure and the confounded sibling comparison OR decreased with an increasing prevalence of exposure. Measures for sharedness of treatments based on Danish health data showed that treatments of chronic diseases have the highest sharedness and treatments of non-chronic diseases have the lowest sharedness. Conclusions Researchers should be aware of the challenge regarding non-shared unmeasured confounding in the sibling comparison analysis, before applying the analysis in non-randomized studies. Otherwise, the sibling comparison analysis may lead to substantial bias.

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了解非共享未测量混杂对兄弟比较分析的影响

背景 同级比较分析用于处理不可测量的混杂因素。先前已经表明，在存在非共享的未测量的混杂因素的情况下，同级比较分析可能会引入显着的偏差，具体取决于未测量的混杂因素的共享性和暴露的共享性。我们的目的是提高对兄弟比较分析这一挑战的认识。方法首先，我们模拟了兄弟姐妹对的暴露、混杂因素和结果。我们模拟了兄弟姐妹对，暴露对结果没有影响，并且存在正混杂。对于不同程度的混杂因素和暴露的共享性以及不同的暴露发生率，我们计算了兄弟姐妹比较优势比（OR）。其次，我们根据丹麦健康数据提供了所选治疗方法的共享措施。结果 混杂同级比较 OR 被可视化，以显示混杂因素和暴露的不同程度的共享性以及不同的暴露发生率。混杂兄弟姐妹比较 OR 随着暴露共享程度的增加而增加，而混杂兄弟姐妹比较 OR 随着暴露发生率的增加而减少。基于丹麦健康数据的治疗共享性衡量标准显示，慢性病治疗的共享性最高，非慢性病治疗的共享性最低。结论 在将分析应用于非随机研究之前，研究人员应该意识到兄弟比较分析中非共享的未测量混杂因素的挑战。否则，同级比较分析可能会导致重大偏差。