Provider Network Structure and Black-to-White Disparity Gaps for Medicare Patients with Diabetes: County-Level Analysis of Cost, Utilization, and Clinical Care

Background: Prior work has shown that provider network structures correlate with outcomes such as patient costs, utilization, and care. However, it remains unknown whether certain provider networks are associated with reduced disparity gaps. Methods: We study the population of Medicare beneficiaries with diabetes who were continuously enrolled in Medicare FFS in 2016. Using multivariable regression analysis of county-level risk adjusted cost, hospitalization, emergency department visits, A1c testing, and preventable diabetes-related hospitalizations, we measure the effect that the relative network connectivity of primary care providers (PCPs) in relation to medical and surgical specialists (PCP/Specialist degree centrality ratio), derived from Medicare patient sharing data, has on non-Hispanic black-to-white disparity gaps controlling for county-level socioeconomic and demographic variables and state fixed effects. Results: Relative to non-Hispanic white, our adjusted results show that non-Hispanic black beneficiaries have $1673 (p<0.001) higher risk adjusted total costs, 2.6 (p<0.001) more hospitalizations (per 1000 beneficiaries), 11.6 (p<0.001) more ED visits (per 1000 beneficiaries), receive 2.2% (p<0.001) less A1c testing, and have 69.4 (p<0.01) more (per 100,000) avoidable diabetes-related hospital admissions. Our main results show that increasing the PCP/Specialist degree centrality ratio by one standard deviation is associated with a disparity gap decrease of 25.3% (p<0.01) in hospitalizations, 8.3% (p<0.05) in ED visits, 2.8% (p<0.01) in A1c testing, and 26.9% (p<0.1) in the volume of preventable diabetes-related hospital admissions. Conclusions: Network structures where PCPs are more central relative to medical and surgical specialists are associated with reduced non-Hispanic black-to-white disparity gaps, suggesting that how we organize and structure our health systems has implications for disparity gaps between non-Hispanic black and white Medicare beneficiaries with diabetes.