The diabetes health plan and medication adherence among individuals with low incomes

OBJECTIVE: To test the impact of the Diabetes Health Plan (DHP), a diabetes‐specific insurance plan that lowers out‐of‐pocket costs for diabetes‐related medications and clinical visits, on adherence to oral hypoglycemic medications among low‐income adults with Type 2 Diabetes (T2DM). DATA SOURCES AND STUDY SETTING: Cohort of adults (18–64) with T2DM, an annual household income <USD 30,000, and who were continuously enrolled in an employer‐sponsored UnitedHealthcare plan for at least two years between 2009 and 2014. STUDY DESIGN: We employed a linear regression Difference‐In‐Differences (DID) approach with a matched comparison group. To assess for differential DHP effects across adherent versus non‐adherent patients, we ran a Difference‐in‐Difference‐in‐Differences (DDD) analysis by including an interaction term that included indicators for DHP exposure status and time, and low versus high baseline medication adherence. DATA COLLECTION: The analytic data set is limited to employer groups that purchased the DHP and standard benefit plans from UnitedHealthcare, had internal pharmacy contracts; complete pharmacy claims data, and sufficient medical claims and lab data to identify employees and their dependents with T2DM. PRINCIPAL FINDINGS: Our DID analysis did not show improved medication adherence associated with employer DHP adoption. However, the DDD model suggested a difference between DHP‐exposed and comparison beneficiaries when comparing the relative effect on individuals who were adherent versus non‐adherent at baseline, as suggested by the significant three‐way interaction term (10.2,p = 0.028). This effect was driven by the 8.2 percentage point increase in medication adherence for the DHP subsample that was non‐adherent at baseline. CONCLUSIONS: The DHP may benefit low‐income patients with low baseline medication adherence. Value‐based insurance design may be an important strategy for mitigating income disparities in T2DM outcomes.