Objectives: Value-Based Insurance Design (VBID) is intended to incentivize the use of services that are most cost-effective for patient care. One strategy is to reduce patient cost-sharing of medications that are crucial for chronic disease, such as inhalers for asthma and/or chronic obstructive pulmonary disease (COPD). Recently, several benefit changes have been introduced into an employee health plan for a large health system in Texas, including co-pay reductions, deductible elimination, and income-based premium subsidies. This study evaluated the impact of these interventions.

Methods: This retrospective, longitudinal study evaluated the impact of a series of benefit changes on medication adherence (PDC, proportion of days covered) using an interrupted time series analysis. Four contiguous study segments were examined between January 1, 2014, and December 31, 2020. This study used existing data from pharmacy claims, pharmacy eligibility, and electronic health records for asthma and/or COPD patients insured through an employee health plan. Adherence to each maintenance inhaler class was evaluated independently (ICS, inhaled corticosteroid; LABA, long-acting beta agonist).

Results: For 469 patients with an ICS-containing inhaler prescription fill, PDC was initially decreasing by 0.0043 (p=0.0005) per month. Immediately after flat co-pay implementation, a PDC increase of 0.0712 (p=0.0147) occurred, and PDC continued to increase by 0.0068 (p=0.0020) per month.

For 339 patients with a LABA-containing inhaler prescription fill, PDC was initially decreasing by 0.0038 (p=0.0029) per month. Immediately after flat co-pay implementation, a PDC increase of 0.0718 (p=0.0180) occurred, and PDC continued to increase by 0.0067 (p=0.0035) per month.

No other interventions had a significant impact on ICS or LABA PDC.

Conclusions: The introduction of a flat co-pay was associated with an increase in adherence for patients using ICS- or LABA-containing maintenance inhalers. Co-pay reductions appear to be more impactful overall when compared with deductible elimination or premium subsidies in this population.