Geographic Variation and Racial Disparities in Novel Glucose-lowering Drugs Adoption Among US Medicare Beneficiaries with Type 2 Diabetes

Background: Newer glucose-lowering drugs (GLDs), i.e., sodium-glucose cotransporter-2 inhibitors (SGLT2i) and glucagon-like peptide-1 receptor agonists (GLP1a), reduce cardiovascular disease (CVD) risk in people with type 2 diabetes (T2D). Prior studies have shown racial disparities in newer GLDs use. However, whether such disparities were modulated by geographic variation in newer GLDs access and how such disparities distribute across the US are unclear.

Methods: Using 2017-2018 claims data from a 15% random nationwide sample of Medicare Part D beneficiaries, we identified patients diagnosed with T2D, received ≥1 T2D medication, and did not use SGLT2i or GLP1a in the year prior to the index date —1/1/2018. Patients were followed up for a year. The cohort was spatiotemporally linked to Dartmouth hospital-referral regions (HRRs) with each patient assigned to 1 of 306 HRRs. We performed multivariable Poisson regression to estimate adjusted initiation rates, and multivariable logistic regression to assess racial disparities in each HRR. The disparity index (non-Hispanic Black/Hispanic vs. non-Hispanic White) of newer GLDs initiation had four levels, corresponding to adjusted odds ratio (aOR) ≤0.5 (p <.05), 0.5<-≤0.9 (p <.05), 0<-≤0.9 (p ≥.05), >0.9, for initiating newer GLDs vs. not among T2D patients.

Results: Among 795,469 patients meeting study criteria, mean (SD) age was 73 (10) y, 53.3% were women, 12.2% were non-Hispanic Black, and 7.2% initiated a newer GLD. In the adjusted model including clinical factors, Medicaid dual eligibility (low-income proxy) was associated with 8% less newer GLDs initiation (incidence rate ratio, 0.92 (95% CI, 0.90-0.94)). Compared to non-Hispanic White patients, non-Hispanic Black (0.66 (0.64-0.68)), Hispanic (0.85 (0.82-0.87)), Asian/Pacific islander (0.94 (0.89-0.98)), and American Indian/Alaska Native (0.74 (0.66-0.82)) patients were less likely to initiate newer GLDs. Significant geographic variation was observed across HRRs, with an initiation rate spanning 2.7%-13.6%. Of 306 regions, 22 have marked racial disparities (disparity index ≤0.5; p <.05), including 57, 70 and 157 regions having disparity index, 0.5<-≤0.9 (p <.05), 0<-≤0.9 (p ≥.05), >0.9, respectively.

Conclusions: Only 7.2% US Medicare beneficiaries with T2D initiated newer GLDs in 2018. Racial disparities are prevalent and striking in nearly half of HRRs across the nation.