The study of racial/ethnic inequalities in health is important to reduce the uneven burden of disease. In the case of colorectal cancer (CRC), disparities in survival among non-Hispanic Whites and Blacks are well documented, and mechanisms leading to these disparities need to be studied formally. It has also been established that body mass index (BMI) is a risk factor for developing CRC, and recent literature shows BMI at diagnosis of CRC is associated with survival. Since BMI varies by racial/ethnic group, a question that arises is whether differences in BMI are partially responsible for observed racial/ethnic disparities in survival for CRC patients. This article presents new methodology to quantify the impact of the hypothetical intervention that matches the BMI distribution in the Black population to a potentially complex distributional form observed in the White population on racial/ethnic disparities in survival. Our density mediation approach can be utilized to estimate natural direct and indirect effects in the general causal mediation setting under stronger assumptions. We perform a simulation study that shows our proposed Bayesian density regression approach performs as well as or better than current methodology allowing for a shift in the mean of the distribution only, and that standard practice of categorizing BMI leads to large biases when BMI is a mediator variable. When applied to motivating data from the Cancer Care Outcomes Research and Surveillance (CanCORS) Consortium, our approach suggests the proposed intervention is potentially beneficial for elderly and low-income Black patients, yet harmful for young or high-income Black populations.

中文翻译：

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体重指数在结直肠癌诊断中对黑人与白人生存差异的作用：密度回归中介方法。


研究种族/族裔健康不平等对于减少疾病负担的不均衡非常重要。就结直肠癌 (CRC) 而言，非西班牙裔白人和黑人之间的生存差异已有充分记录，并且需要正式研究导致这些差异的机制。还已确定，体重指数 (BMI) 是发生 CRC 的危险因素，最近的文献显示，诊断 CRC 时的 BMI 与生存相关。由于 BMI 因种族/民族群体而异，因此出现的一个问题是 BMI 差异是否是观察到的 CRC 患者生存率种族/民族差异的部分原因。本文提出了新的方法来量化假设干预措施的影响，该假设干预措施将黑人群体中的 BMI 分布与白人群体中观察到的潜在复杂分布形式相匹配，对种族/民族生存差异产生影响。我们的密度中介方法可用于在更强的假设下估计一般因果中介环境中的自然直接和间接影响。我们进行了一项模拟研究，表明我们提出的贝叶斯密度回归方法的性能与仅允许分布均值发生变化的当前方法一样好甚至更好，并且当 BMI 为中介时，对 BMI 进行分类的标准做法会导致较大偏差多变的。当应用于癌症护理结果研究和监测 (CanCORS) 联盟的激励数据时，我们的方法表明，拟议的干预措施可能对老年和低收入黑人患者有益，但对年轻或高收入黑人群体有害。