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.
Scenario One: SES is a confounder
In the United States, racialized women have a higher prevalence of gestational diabetes, leading to disparities between whites and women from other racial groups. Furthermore, gestational diabetes is a risk factor for cardiovascular disease later in life, so we also see subsequent racial disparities in cardiovascular disease up to 25 years after delivery. Consider a hypothetical study, with the goal of better understanding racial disparities in cardiovascular disease among women who had a pregnancy complicated by gestational diabetes. In the analysis stage, controlling for SES would be necessary as it confounds the relationship between gestational diabetes and cardiovascular disease. SES (e.g. income, diet, and neighborhood) is related to both the exposure and outcome in this scenario, and is not on the pathway between the two. In terms of interpretation, after adjustment for this factor during the analysis, we could say that our findings are adjusted for the confounding effect of SES.
Scenario Two: SES as an effect modifier
Maternal infections during pregnancy can have adverse effects on birth outcomes, notably low infant birth weight. Pregnant women often use antibiotics to treat these infections, and a known side effect is potentially increased infant birthweight. Similarly to scenario one, there are stark disparities in the prescription of antibiotics as well as the occurrence of low birth weight deliveries across racial groups. When studying the relationship between antibiotic use and the incidence of low birthweight in a racially diverse population, we can analyze SES as an effect modifier of the relationship. For example, if low-SES pregnant women of color have more underlying infections, they may benefit more from antibiotic use compared to women with high-SES. In this example, if the results show that the low-SES women of color do in fact benefit more from antibiotic use, then we can say that SES modifies the relationship between antibiotic use and low birthweight.
Scenario Three: SES as a mediator
In the United States, significant racial and ethnic disparities in maternal mortality and morbidity exist; markedly, Black women are 3 to 4 times more likely to die due to a pregnancy-related complication, compared with white women. However, there is considerable heterogeneity in these outcomes when we stratify Black women by their nativity (i.e. place of birth). For example, previous studies show that African-born and Caribbean-born Black American women have lower risk of preterm birth and infant mortality. In one of my current research projects, I am studying the relationship between maternal nativity and adverse birth outcomes among Black women in California. In this study, we will be analyzing SES as a mediator of the relationship between nativity and adverse birth outcomes. We are interested in seeing how much of this protective effect of being born outside of the United States is mediated through SES (e.g. immigrant Black women may have higher education, income etc.).
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.
Continuing my example from scenario three (above), a secondary research question for my maternal nativity paper is to try and understand how instrumental and emotional social support (e.g. support from family members with household duties during and after pregnancy) may mediate the relationship between nativity and adverse birth outcomes. I will try to use Oaxaca-Blinder decomposition methods to understand the extent to which social support explains the disparities in adverse birth outcomes among foreign-born and US-born Black women.