Does the diabetes health plan have a differential impact on medication adherence among beneficiaries with fewer financial resources?

BACKGROUND: The Diabetes Health Plan (DHP), a value-based insurance plan that reduces cost sharing, was previously shown to modestly increase employer-level medication adherence. It is unclear how the DHP might impact individuals with different incomes. OBJECTIVE: To examine the impact of the DHP on individual-level medication adherence, by income level. METHODS: This is a retrospective, quasiexperimental study. An employer-level propensity score match was done to identify suitable control employers, followed by individual-level propensity score weighing. These weights were applied to difference-in-difference models examining the effect of the DHP and the effect of income on changes in adherence to metformin, statins, and angiotensin-converting enzymes/angiotensin receptor blockers. The weights were then applied to a differences-in-differences-in-differences model to estimate the differential impact of DHP status on changes in adherence by income group. RESULTS: The study population included 2,065 beneficiaries with DHP and 17,704 matched controls. There were no significant differences in changes to adherence for any medications between beneficiaries enrolled in the DHP vs standard plans. However, adherence to all medications was higher among those with incomes greater than $75,000 (year 1: metformin: +7.3 percentage points; statin +4.3 percentage points; angiotensin-converting enzymes/angiotensin receptor blockers: +6.2 percentage points; P < 0.01) compared with those with incomes less than $50,000. The differences-in-differences-in-differences term examining the impact of income on the DHP effect was not significant for any comparisons. CONCLUSIONS: We did not find significant associations between the DHP and changes in individual-level medication adherence, even for low-income beneficiaries. New strategies to improve consumer engagement may be needed to translate value-based insurance designs into changes in patient behavior.