The original NEXT-D Network developed a conceptual framework to help researchers and policy makers carefully consider the wide spectrum of programs and policies that might impact T2D prevention as well as diabetes management and outcomes [20•, 36]. We placed each of the NEXT-D3 studies into this framework (Fig. 1). The figure shows the primary approach of each of the studies and does not capture any additional effects the studies may have within the conceptual framework. Of the six participating research centers, one of them (Northwestern University) is studying two distinct natural experiments and therefore is represented by two letters within two different circles on the figure (B and C). Programs can be implemented by and within individual health systems, represented by the innermost blue circle. Other programs are initiated by suppliers and purchasers of health care, such as private employers and private or public health insurers, represented by the next surrounding white circle. Depicted in the third light green circle are institutions in the broader community, including religious, social service, civic, and commercial organizations that provide resources for and support programs designed to prevent T2D or to improve diabetes care; none of the NEXT-D3 studies are currently in this realm. Finally, the laws and regulations that shape the economic, physical, social, and cultural environments of Americans with or at risk for diabetes are represented in the outermost dark green circle.

Fig. 1

Conceptual framework for NEXT-D3

As mentioned above, a key feature of NEXT-D3 is an explicit focus on SDOH and health equity. The World Health Organization defines SDOH as the “complex, integrated, and overlapping social structures and economic systems (e.g., the social environment, physical environment, health services, and structural and societal factors) that are responsible for most health inequities (disparities) around the world” [37]. In NEXT-D2, the research teams began to advance the knowledge base of how rigorously evaluated population-based programs or policy changes can influence disparities in T2D prevalence and diabetes outcomes [38], and NEXT-D3 aims to continue this in a more explicit and focused way, with some projects directly intervening on SDOH. A NEXT-D3 subcommittee, comprised of representatives from each study site, is also working to develop a set of standardized and validated SDOH measures that can be used across the network.

Below, we describe the individual research projects being conducted by NEXT-D3 researchers, each of which focuses on T2D prevention or treatment of diabetes and/or its complications (Table 1). Each project evaluates a policy or program using specific, well-defined research questions and employs natural experiment research design to reduce bias from confounding, such as controlled pre/post or interrupted time series. The projects fall under three major themes: health insurance expansion, health care financing and payment models, and health care and policy innovations to address SDOH.

Table 1 Selected characteristics of NEXT-D3 projects Health Insurance ExpansionEffects of Insurance Expansion Under the ACA on Medium and Long-Term Diabetes Diagnosis, Severity, Health Outcomes, and Costs (Northwestern University, Part 1)

The first part of the Northwestern University projects will examine the effects of insurance expansion on diabetes-related outcomes. The ACA substantially reduced the number of uninsured persons, especially in Medicaid expansion states and among poorer segments of the population, who were more likely to be uninsured prior to the ACA [39]. Understanding the health and economic effects of Medicaid expansion can inform policies for diabetes care, for other chronic conditions where outcomes can be affected by improved access to care and medical management, and for potential reduction of disparities in health outcomes. The Northwestern study will examine the medium- and long-term effects of gaining insurance under the ACA, both through Medicaid expansion and under the individual insurance exchanges, on diabetes diagnosis, treatment, severity, health outcomes, and costs.

Assess Insurance Coverage Expansion on Diabetes Complications (ACE-D, Oregon Health & Science University)

Analyses of the short-term impact of Medicaid expansion demonstrated increased access to preventive care and improved management of T2D [40,41,42]. However, there is limited information on the longer-term effects of Medicaid expansion or the health outcomes for patients who gain and lose Medicaid coverage due to changes in Medicaid eligibility. The Oregon Health & Science University study will analyze data from over 280,000 patients within the national ADVANCE (Accelerating Data Value Across a National Community Health Center Network) clinical research network of community health centers, comparing outcomes for patients from states that expanded Medicaid with outcomes for patients from states that did not expand Medicaid, as well as examining patients with continuous insurance coverage, unstable insurance coverage, and no insurance coverage. Outcomes will include acute and chronic diabetes-related complications as well as mortality. The analyses will also assess whether individual-level and/or community-level SDOH moderate the relationship between Medicaid expansion and health outcomes.

Health Care Financing and Payment ModelsLong-Term Impact of Reduced Patient Out-of-Pocket Costs on Diabetes Complications (Harvard University)

HDHPs that require patients to pay up to $1000–7000 out of pocket (OOP) per year are now the predominant private health insurance arrangement [43]. Increased OOP costs under HDHPs are associated with delays in seeking care [16, 27], increases in acute, preventable diabetes complications [16], and increases in high-severity emergency department visits among low-income HDHP members [17]. HDHPs with health savings accounts (HSA-HDHPs) typically make antidiabetic and other cardioprotective medications subject to the full deductible. For example, the average HSA-HDHP insulin user pays $700–1000 per year for the medication, 2–3 times more than those without an HAS-HDHP account [44]. Because of concerns about such cost barriers, an increasing number of employers are purchasing preventive drug lists (PDLs) that lower OOP costs for cardioprotective medications or are switching from an HDHP to more generous lower-deductible health plans [26]. The Harvard site’s NEXT-D2 study found that PDLs increase short-term cardioprotective medication use, especially among low-income HDHP members. PDLs that reduce medication cost may prevent rationing and underuse of antiglycemic medications among low-income HDHP members [26]. In NEXT-D3, Harvard will analyze a 16-year rolling cohort using a combination large commercial and Medicare Advantage health insurance claims database with members from all 50 states and the District of Columbia. Applying an interrupted time series with comparison series difference-in-difference design, the team will determine whether adopting employer PDLs or switching from HDHPs to low-deductible plans is associated with long-term reductions in acute and chronic diabetes complications, including among low-income and high-morbidity members. Finally, the team will assess the effect of state policies that reduce insulin OOP costs on insulin use and diabetes complications.

Effects of Medicaid Coverage and State-Level Delivery Approaches on Health Care Quality, Outcomes, and Costs for Adults with Diabetes (Northwestern University, Part 2)

The second part of the Northwestern project focuses on state-level variation in Medicaid managed care policies that shape access to newer classes of diabetes medications, such as sodium-glucose cotransporter-2 (SGLT2) inhibitors, which have unique protective health benefits but are significantly more costly. State Medicaid agencies steward limited public resources while attempting to balance access, quality, outcomes, and cost in their Medicaid programs, particularly for patients with costly chronic conditions such as diabetes. Most states administer Medicaid programs in partnership with managed care organizations, and policies to balance access to costlier medications are enacted by both the Medicaid agency and managed care partners in ways that differ in virtually every state [45]. This study will integrate Medicaid managed care administrative data from multiple states to compare effects on medication starts, acute diabetes complications, and net health care costs as different state programs enact policies that are designed to lower barriers for the initiation and use of SGLT2 inhibitors (e.g., relaxing prior authorization requirements; extending refill quantity limits from 30 to 90 days). It is anticipated that this natural experiment will help states and managed care partners identify select policy approaches that may increase pharmaceutical costs for patients with diabetes by expanding access to SGLT2 inhibitors, but by doing so, result in more favorable and equitable health outcomes, as well as lower overall diabetes-related health expenditures, particularly for vulnerable patients at the highest risk for avoidable cardiovascular and renal complications.

Louisiana Experiment to Address Diabetes: Zero-Dollar Copayment (LEAD-ZDC) for Improving Disease Management (Tulane University)

Nonadherence to prescribed antidiabetic medications, antihypertensives, and statins is associated with poorer glycemic control, increased risk of diabetes complications, and greater health care costs [46]. While patients have various reasons for nonadherence, one of the primary reasons is because they cannot afford their medications [46]. Cost-related nonadherence has been closely linked to SDOH, including food insecurity and financial burden [47]. Blue Cross and Blue Shield of Louisiana has instituted a value-based benefit design (in which health insurance is structured in a way that incentivizes and drives patients and providers toward the most valuable services: those with the most benefit relative to cost) with zero-dollar copayments for selected prescription medications for its fully insured members [46]. This study will evaluate the effects of the zero-dollar copayment (ZDC) program on medication adherence, glycemic control, rates of diabetes complications, and health care utilization using claims and electronic health records (EHR) data. Additionally, the study will examine barriers and facilitators influencing how the program is implemented and perceived by patients and health care providers. Lastly, these analyses will examine the short-term cost-effectiveness of the zero-dollar copayment program from both health system and societal perspectives and will use simulation approaches to model cost-effectiveness over a 40-year time period.

Health Care and Policy Innovations to Address SDOHA Pragmatic Nationwide Randomized Controlled Trial of Coordinated Medical, Behavioral, and Social Services to Improve Care and Utilization Among High-Cost, High-Need Insured Patients with Diabetes (University of California Los Angeles)

University of California Los Angeles and UnitedHealthcare (UHC) are partnering to evaluate a national care coordination program for high-cost, high-need commercially insured UHC members. This care coordination program was launched in 2015 and aims to provide “whole-person care,” integrating intensive medical, behavioral, and social support at a community level to address barriers to access in addition to SDOH, including food and housing insecurity. UHC designed and instituted a patient-level, pragmatic randomized controlled trial (RCT) of this program and has randomized over 500,000 individuals to either the national care coordination program or usual care. Using administrative claims data, this study will analyze the effects of this program on multiple outcomes using an intention-to-treat RCT analysis as well as an instrumental variable analysis with randomization status as the instrument. These analyses will evaluate whether the program is associated with reductions in diabetes complications, acute care utilization, and costs of care.

Longitudinal Food security Experiments via Supplemental Assistance with Nutrition for Diabetes (LIFESPAN-D, University of California San Francisco)

Food insecurity is a common and potent mediator in the development of T2D and diabetes-related complications among low-income populations in the USA [48]. Food insecurity pressures low-income individuals with T2D to consume inexpensive food of poor dietary quality, presenting difficult choices between paying more for higher-quality food or paying for medicine or other expenses such as housing or heat [49,50,51]. Furthermore, food insecurity among pregnant women is associated with an increased risk of gestational diabetes and other pregnancy-related complications [52]. Longitudinal Food security Experiments via Supplemental Assistance with Nutrition for Diabetes (LIFESPAN-D) is composed of two substudies. The first substudy relates to older low-income adults. In 2019, California began to allow low-income, older, and/or disabled individuals receiving Supplemental Security Income (SSI)—populations with a high prevalence of food insecurity and risk for T2D and diabetes complications—to receive simultaneous benefits from the Supplemental Nutrition Assistance Program (SNAP, formerly known as food stamps). This substudy will harmonize and analyze statewide longitudinal datasets (including hospital discharge data) using a quasi-experimental pre/post design to determine whether the addition of the SNAP benefit for older low-income adults is associated with county-level reductions in multiple outcomes, including diabetes-related hospitalizations, individual-level improvements in cardiometabolic control among individuals with T2D, and reduced incidence of T2D among individuals with prediabetes. The second substudy will evaluate the effects of a separate policy that allowed recipients of the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC)—a program that provides nutrition support to low-income pregnant and postpartum women and children under the age of 5—to receive an electronic benefit card rather than paper vouchers. The substudy will examine whether this policy change leads to increased WIC benefit uptake and reductions in gestational diabetes and other pregnancy-related complications among pregnant women and in unfavorable birth outcomes associated with diabetes risk in their children such as low birth weight.