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

Abstract

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.

Keywords: diabetes; health disparities; health equity; low-income; medication non-adherence; value based insurance design.