Disparities in the Use of New Diabetes Medications: Widening Treatment Inequality by Race and Insurance Coverage

Abstract

• Issue: Diabetes has a well-documented association with race and socioeconomic status; for example, the condition’s prevalence is significantly higher in Black versus white communities. This disparity may be exacerbated by treatment disparities, including differences in use of diabetes medications introduced since 2005.
• Goals: Examine trends and disparities in use of and expenditures for three new classes of diabetes drugs (glucagon-like peptide-1 receptor agonists, dipeptidyl peptidase 4 inhibitors, and sodium-glucose cotransporter-2 inhibitors) by race, ethnicity, insurance coverage, education, and income.
• Methods: Analysis of Medical Expenditure Survey (MEPS) data from 2003 to 2019.
• Key Findings: Disparities in use between Black and white adults emerged soon after the drugs’ introduction, controlling for trends by insurance status, income, and education. These disparities widened significantly through 2019. Drug usage rates for Latinx/Hispanic people fall midway between rates for white and Black people. Similar disparities by insurance coverage also emerged shortly after the drugs became available and continue today. In addition, lower socioeconomic status has been independently associated with lower take-up of new medications. Disparities in spending are small in magnitude but increasing as use of these drugs grows.
• Conclusions: Efforts to narrow disparities in diabetes outcomes should account for the impact of disparate access to advances in diabetes treatment.

Introduction

Substantial and persistent disparities in health outcomes exist among people with diabetes by race, ethnicity, income, occupation, and other measures of socioeconomic status.¹ These disparities are of particular concern because diabetes is one of the most common chronic conditions in the United States, affecting 13.4 percent of the adult population.²

Most research on disparities in diabetes has focused on the impact of underlying social determinants of health, such as food and housing, which affect the incidence of diabetes.³ But income, race, ethnicity, and other measures of socioeconomic status also affect outcomes among those who have been diagnosed with the condition. These outcome disparities may arise, in part, because of differences in access to effective diabetes treatment. Studies focused on access to effective diabetes treatments have demonstrated that provider- and organization-level interventions can generate outcome improvements through consistent follow-up, better communication with patients (including through community health workers), care coordination, and similar practices.⁴

The challenge of reducing disparities is, however, ongoing and dynamic. The introduction of new technologies and treatments is often linked to increasing disparities.⁵ Therefore, innovations in diabetes treatment, including the introduction of new pharmaceutical therapies that offer better or easier glycemic control or reduce the sequelae of diabetes, could exacerbate inequalities. The association between new treatments and disparities can arise because of a lack of financial access to new, more costly therapies.⁶ However, disparities in the use of new treatments, particularly by education status, are also found in countries with few financial barriers to access.⁷

Between the discovery of insulin in the early 1920s and the mid-1990s, there were few advances in pharmacological treatment of diabetes. In the past 25 years, however, nine new drug classes for diabetes treatment have been introduced.⁸ Three of these classes, introduced since 2005, demonstrate high efficacy and fewer side effects, particularly for type 2 diabetes:⁹ glucagon-like peptide-1 receptor agonists (GLP-1 RA); dipeptidyl peptidase 4 inhibitors (DPP4-i); and sodium-glucose cotransporter-2 inhibitors (SGLT2-i).

These drugs remain on patent and have high retail prices.¹⁰ In addition, drug companies now offer new combinations of agents in fixed doses; these formulations make adherence to therapy easier.¹¹ Use of these new drugs has increased rapidly since their approval by the U.S. Food and Drug Administration (FDA).¹² However, prior research has shown racial and ethnic disparities in the use of these drugs, after controlling for people’s income and health insurance.¹³ Appendix Exhibit 1 describes overall trends in the use of drugs for diabetes control.

Recent policy action around diabetes care has focused on the cost of insulin. In this issue brief, we turn attention to three new classes of drugs used in the care of people with diabetes. Using 2003–2019 data from the Medical Expenditure Panel Survey (MEPS), we examine whether treatment disparities are widening contemporaneously with the introduction of new diabetes medications. (See “How We Conducted This Study” for further detail.)

Key Findings

Disparities in New Medication Utilization

Between the periods 2003–2006 and 2017–2019, the adjusted average use rate of the three new medication classes (GLP-1 RA, DPP4-i, and SGLT2-i) we examined increased from 2 percent to 22 percent among adults with diabetes. Over time, however, disparities by race, education, income, and insurance in the use of these diabetes medications have emerged. By 2010–2013, Black adults with diabetes were about 4 percentage points less likely than white adults to use these new medications, a disparity of 27 percent (controlling for trends by household income, insurance coverage, and educational status, as well as other covariates). The magnitude of the disparity remained roughly constant through 2017–2019. Latinx/Hispanic adults with diabetes had use rates midway between white and Black patients.

Patients enrolled in private group insurance are much more likely to use one of three new medications to treat diabetes than others (controlling for trends by race, ethnicity, income, education, and other covariates). The gap in use by insurance coverage type emerged almost immediately after the drugs were introduced and continues through today (Exhibit 2). Uninsured patients and those who hold traditional Medicare without any supplemental coverage have the lowest rates of use. Patients with Medicaid or Medicare plus other coverage (traditional Medicare with supplemental coverage, Medicare Advantage, or Medicaid) have rates of use midway between the uninsured and those with private coverage.

Individuals with a bachelor’s degree or higher are more likely to initiate new diabetes medications to control their glucose levels than others (Appendix Exhibit 2). However, by 2017–2019, these differences were relatively small (controlling for trends by race, ethnicity, income, insurance, and other covariates), suggesting that financial access, rather than care-seeking behavior, is the more important determinant of outcomes.

We find relatively little evidence that income itself has an impact on rates of new medication utilization, either initially or over time (controlling for trends by race, ethnicity, insurance, education, and other covariates) (Appendix Exhibit 2). Differences in rates of use by income are quite small and not always statistically significant. In general, however, households with incomes between 125 percent and 199 percent of the federal poverty level — just above the Medicaid cutoff under the Affordable Care Act — have lower use rates of new medications than those in lower and higher income groups.

Expenditures on Diabetes Medications

Overall, total inflation-adjusted expenditures on diabetes medications increased over time, driven mainly by increased spending on insulin, which is both costly and widely used. Insulin accounted for a quarter of average spending on diabetes medications in 2003–2006 and 54 percent in 2017–2019. Across all groups (race and ethnicity, insurance, income, education), expenditures on diabetes medications were similar in the first two periods (2003–2006 and 2007–2009). However, disparities begin to emerge after 2009 (Appendix Exhibit 3).

Disparities were driven by trends in spending on insulin and on the new classes of diabetes medications GLP-1 RA, DPP4-i, and SGLT2-i. There were few disparities in spending on older noninsulin medications, such as metformin (Appendix Exhibit 4). Overall inflation-adjusted spending on older noninsulin medications declined from $772 to $332 (2019 dollars) over time.

Disparities by Insurance Coverage

Total spending on diabetes medications has always been lower for uninsured people than for people with coverage, but this disparity widened substantially over time. By 2017–2019, uninsured people with diabetes were spending about 40 percent less per year on diabetes medications than those with private insurance coverage or with Medicare plus supplemental insurance coverage (controlling for trends by race, income, education, and other covariates).

Part of the reason for this widening disparity between the uninsured and insured may be that those people with diabetes most in need of costly medications were more likely to seek out newly available coverage under the Affordable Care Act, leaving an uninsured population that was relatively less ill. However, disparities among people with different types of coverage also grew over this period. By 2017–2019, spending among those with Medicaid or Medicare without additional coverage was only about three-quarters as high as among those with private coverage (Exhibit 3).

Disparities by Race

Disparities by race also grew over time (controlling for trends by income, insurance, education, and other covariates). By 2017–2019, total spending on diabetes medications was about $500 to $700 more per year for white Americans with diabetes than for their Latinx/Hispanic or Black counterparts, a disparity of 16 percent to 22 percent (Exhibit 4).

Disparities in Spending on Insulin and New Diabetes Medications

An important source of these growing disparities in spending was the increases in insulin prices. Prior research has shown that the retail price of insulin rose rapidly between 2010 and 2016.¹⁴ We find that, among people using insulin, total spending nearly doubled ($724 vs. $1,347), even though the number of users remained constant (28% of the population). The observed pattern of disparities in insulin spending emerged in this period as spending per user increased.

However, between 2016 and 2019, disparities in insulin expenditures — by race, ethnicity, insurance, education, and income — remained relatively constant. Instead, the increased disparities seen in overall spending on diabetes medications were the result of growing differences in spending on new drugs, such as GLP-1 RA, DPP4-i, and SGLT2-i. While total spending on these medications was well below spending on insulin (in part because relatively few people were taking them), the difference in average expenditures among groups widened considerably since 2014.

Expenditures on New Diabetes Medications by Coverage

Spending for new diabetes medications has always been higher for individuals with private coverage than other groups, especially uninsured individuals. Between 2014–2016 and 2017–2019, the covariate-adjusted spending disparity between individuals with private insurance and those who are uninsured increased from 44 percent to 54 percent. Compared to individuals with private insurance coverage, people with Medicare have a similar spending trend if they have supplemental coverage or are enrolled in Medicare Advantage. Otherwise, their spending is about two-thirds that of people with private insurance.

Expenditures on New Diabetes Medications by Race

Trends in annual expenditures on new medications by race also diverged over time (controlling for income, insurance, education, gender, and other covariates). The difference in spending between Black and white Americans increased from $211 in 2014–2016 to $351 in 2017–2019, a disparity of 30 percent. Spending on new medications is also lower for Latinx/Hispanic patients than for white patients, with a 16 percent disparity by 2017–2019 (Appendix Exhibit 5).

Policy Implications

Our research suggests that there are growing differences in access to new diabetes medications across patient populations. One key difference is by insurance coverage. The first important step to reducing disparities in access to novel pharmaceuticals is ensuring that all people with diabetes hold comprehensive coverage that includes these therapies.

But insurance coverage is not enough. We observe persistent and widening disparities in use of new diabetes medications by race and ethnicity, after adjusting for trends by income, education, and insurance. More actions will be needed to address the barriers that Black and Latinx/Hispanic patients face, potentially including direct outreach to physicians.