Historic Residential Redlining and Diabetes: Mediating Pathways and Policy Solutions Free

Historic residential redlining refers to the practice of systematically denying services such as credit access and insurance for residents of certain neighborhoods, primarily based on the racial and ethnic makeup of those neighborhoods (1–5). In 1933, the federal government codified these practices into their own New Deal lending via the creation of the Homes Owners’ Loan Corporation (HOLC) (4) and its development of residential security maps that graded neighborhoods on a color-coded scale (A or green is best; B or blue is still desirable; C or yellow is definitely declining; and D or red is hazardous). It is from this practice, and these maps, that the term “redlining” was derived, as neighborhoods colored red were deemed the least desirable, and, in turn, least deserving of credit and insurance. While the Civil Rights Acts of 1964 and the Fair Housing Act of 1968 sought to prohibit explicit redlining, a growing literature has documented the persistent negative impact that redlining has had, and continues to have, on community- and individual-level health and diabetes outcomes (6–10). Related to diabetes outcomes specifically, prior work has noted associations, as well as pathways, connecting historic redlining practices to increased prevalence rates of diabetes (8) and to increased diabetes-specific mortality risk (9).

It is to this growing body of work that the research article by Umer et al. contributes (11). In their article in this issue of Diabetes Care, the authors examine whether historic redlining is associated with gestational diabetes mellitus (GDM) and whether an individual’s BMI and the deprivation of their immediate neighborhood act as significant mediators. Drawing on pregnancy and BMI data from Kaiser Permanente Southern California’s health records between 2008 and 2018, their study found that (compared with residents in A-graded areas) the adjusted risk of GDM was 20% higher among individuals residing within historically B-graded neighborhoods, 22% higher among those residing within C-graded neighborhoods, and 30% higher in historically D-graded neighborhoods. The authors further show that 44.2% of these associations were mediated via prepregnancy BMI and 64.5% via the area deprivation index of the area within which the individuals reside. This study has several notable strengths. First, it leveraged unique electronic health records data with individual-level pregnancy data spanning mothers from a diverse set of sociodemographic backgrounds. The use of individual-level data is an important contribution to the existing literature, as most prior studies have used aggregate community-level data to examine associations between historic redlining exposure and health and diabetes outcomes (although exceptions exist, such as, e.g., Linde and Egede [10]). Second, in line with other recent work (see, e.g., Egede et al. [8]), this study goes beyond an examination of the association between historic redlining and present-day GDM disparities by probing the factors that mediate these pathways. The identification of mediating pathways is critical for the development of targeted policy solutions aiming to counteract the persistent negative effects of historic redlining upon present-day GDM outcomes. While the study has several strengths, it also has limitations that need to be acknowledged. First, as noted by the authors, the observational study design means that findings are indicative of associations, not causal effects. Second, since present-day census areas do not perfectly map into historic HOLC designations, there is a possibility for measurement error from misclassification. Third, given the limited geographic scope of this study (Southern California), findings may not generalize to other U.S. cities.

With study limitations noted, it is worth also noting that when taken in the context of prior studies, the overall message of the literature is becoming increasingly clear: historic redlining appears to have a robust negative impact on diabetes prevalence and diabetes-related health outcomes. Furthermore, the work by Umer et al. (11), as well as others (8), shows that the identification of mediating pathways is key for the purpose of finding a tangible path forward. This is because mediating pathways identify present-day pathways that may be amenable to policy intervention. We and others are examining these pathways and the relative potency of different policy solutions in research supported by the National Institute on Minority Health and Health Disparities. However, there are several policy domains that have been noted as particularly critical for policy action. These domains pertain to housing, education, health care, economic empowerment, the built environment, and food (Fig. 1) (4,9,12–15).

Given the potential importance of policy for the reversal of persistent negative effects due to historic redlining, we briefly summarize some of the effects here, drawing on the policy path forward outlined in Egede et al. (4). Pertaining to the negative effects that historic redlining has had on the housing environment of affected areas, investments in structural housing repairs (via home improvement tax credits), expanded use and funds for targeted community development block grants, and zoning reforms that enable mixed-income housing projects are all potential levers for addressing persistent negative effects. To reduce persistent structural inequities in education, continued and expanded investments in early childhood programs such as the Head Start program represent a particularly high-yield strategy. More broadly, policymakers ought to also consider revising existing school funding systems to ensure these are independent of the local tax base, which currently further perpetuates resource inequities across public schools. In health care, expanding access (e.g., via Medicaid expansion within nonexpansion states) and revising value-based health system payments to also incentivize addressing patients’ social needs appear particularly important to ensuring our health care systems are part of the solution to longstanding structural inequities. The economic empowerment of historically redlined neighborhoods can further be stimulated by state and/or local minimum wage increases and/or via targeted tax benefits for employers within historically affected communities. The residents within these communities can also be benefitted via direct investments into their built environment, for example, via state or local complete street regulations that help in the development of walkable and bikeable neighborhoods and/or via the incentivizing of local greenspace developments. Lastly, the food security of residents can be improved via policies such as a broadening of Supplemental Nutrition Assistance Program (SNAP) coverage and/or via tax incentives targeting the development and opening of supermarkets that can help offer healthy food options.

To summarize, the article by Umer et al. (11) represents an important contribution to the broader literature on the effects of historic redlining and to the more recent and limited literature concerned with the identification of pathways that continue to perpetuate the negative effects of historic practices of structural racism. While more research is still needed, we also call attention to the importance of work that helps translate research insights about pathways into concrete policy solutions. The path forward, as we see it now, is one where concrete policy solutions work to eliminate the persistence of these pathways. As noted, this will require future research but also further determination and action from local, state, and federal policymakers.