1. Give an example of a research question for investigating racial/ethnic health disparities where: [1] SES is a confounder; [2] SES is an effect modifier; [3] SES is a mediator. Briefly discuss the interpretations/implications of each approach as it relates to understanding health disparities by race/ethnicity.
SES as a confounder: Does regular exercise reduce the risk of kidney disease? In this example, SES may directly affect likelihood of exercise (e.g. access to safe neighborhoods, gym affordability, etc.) and SES is also linked to kidney disease through causal pathways outside of exercise. The answer this question to find a direct causal pathway between exercise and kidney disease diagnosis must be understood in the context of SES—if a causal relationship is suspected, the onus is on public health officials to find ways to equalize opportunities to take part in this risk reducing behavior.
SES as an effect modifier: Does screening for hypertension reduce the incidence of chronic kidney disease? This research question is predicated on the idea that hypertension leads to kidney disease and that diagnosing hypertension will lead to treatment, thus reducing the rate of CKD. SES may act as an effect modifier by influencing access to care for ongoing treatment of hypertension and the ability to afford antihypertensive medications. This relationship highlights the importance of SES as a determinant of health outcomes through disparities in access to medical care/treatments.
SES as a mediator: Is educational attainment associated with risk of end-stage kidney disease? Since education drives SES and SES then drives multiple risk factors for ESKD, SES acts as a mediator along the causal pathway. The strong relationship between education and SES implies the importance of strong education programs to address social inequalities (though it should be noted that the simple education à SES framework ignores other societal dynamics, namely the effect of structural racism).
2. Describe a potential effect modifier, mediator, or contextual variable (for definition of contextual variable, see Diez-Roux reading) for an association of interest to you and relevant to health disparities. For example, for investigating the association between education and hypertension, I might be interested in evaluating whether the association between years of education and hypertension is different for Black men than for White men. Describe how you would study whether this relationship exists.
Given the existing racial disparity in end stage kidney disease (ESKD) incidence, it is important to understand the effectiveness of various therapies aimed at slowing the progression of chronic kidney disease. ACE inhibitors and ARBs are key therapies for proteinuric kidney disease. Since race and SES play a role in access to care and likelihood of receiving optimal therapies, I would be interested to see if some of the difference between the rates of ESKD between Black and White patients may mediated by different rates of ACE inhibitor/ARB use in proteinuric CKD in these groups.