Nguyen Thu T, Tchetgen Tchetgen Eric J, Kawachi Ichiro, Gilman Stephen E, Walter Stefan, Glymour M Maria
From the aDepartment of Epidemiology & Biostatistics, University of California, San Francisco, CA; bDepartment of Biostatistics, cDepartment of Epidemiology, dDepartment of Social and Behavioral Sciences, Harvard T.H. Chan School of Public Health, Boston, MA; and eDivision of Intramural Population Health Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD.
Epidemiology. 2016 Sep;27(5):670-6. doi: 10.1097/EDE.0000000000000517.
Inverse odds ratio weighting, a newly proposed tool to evaluate mediation in exposure-disease associations, may be valuable for a host of research questions, but little is known about its performance in real data. We compare this approach to a more conventional Baron and Kenny type of decomposition on an additive hazards scale to estimate total, direct, and indirect effects using the example of the role of literacy in mediating the effects of education on mortality.
Health and Retirement Study participants born in the United States between 1900 and 1947 were interviewed biennially for up to 12 years (N = 17,054). Literacy was measured with a brief vocabulary assessment. Decomposition estimates were derived based on Aalen additive hazards models.
A 1 standard deviation difference in educational attainment (3 years) was associated with 6.7 fewer deaths per 1000 person-years (β = -6.7, 95% confidence interval [CI]: -7.9, -5.4). Of this decrease, 1.3 fewer deaths (β = -1.3, 95% CI: -4.0, 1.2) were attributed to the literacy pathway (natural indirect), representing 19% of the total effect. Baron and Kenny estimates were consistent with inverse odds ratio weighting estimates but were less variable (natural indirect effect: -1.2 [95% CI: -1.7, -0.69], representing 18% of total effect).
In a cohort of older Americans, literacy partially mediated the effect of education on mortality. See Video Abstract at http://links.lww.com/EDE/B78.
逆比值比加权法是一种新提出的用于评估暴露-疾病关联中介作用的工具，可能对许多研究问题具有重要价值，但对于其在实际数据中的表现知之甚少。我们以识字率在教育对死亡率影响的中介作用为例，在相加风险尺度上，将这种方法与更传统的Baron和Kenny分解法进行比较，以估计总效应、直接效应和间接效应。
对1900年至1947年在美国出生的健康与退休研究参与者进行了长达12年的每两年一次的访谈（N = 17,054）。通过简短的词汇评估来测量识字率。基于Aalen相加风险模型得出分解估计值。
教育程度相差1个标准差（3年）与每1000人年死亡人数减少6.7例相关（β = -6.7，95%置信区间[CI]：-7.9，-5.4）。在这一减少的死亡人数中，有1.3例死亡（β = -1.3，95% CI：-4.0，1.2）归因于识字途径（自然间接效应），占总效应的19%。Baron和Kenny估计值与逆比值比加权估计值一致，但变异性较小（自然间接效应：-1.2 [95% CI：-1.7，-0.69]，占总效应的18%）。
在一组美国老年人中，识字率部分介导了教育对死亡率的影响。见视频摘要：http://links.lww.com/EDE/B78 。
