Changes in Persistence to Basal Insulin Following the Medicare Out-of-Pocket Cost Cap

OBJECTIVE: To evaluate changes in persistence to basal insulin following the implementation of the $35 monthly out-of-pocket cost cap for insulin for Medicare beneficiaries. STUDY DESIGN: We completed a retrospective cohort analysis of a nationally representative Medicare Advantage sample from 2022 to 2023. METHODS: We compared precap rates of persistence to basal insulin in 2022 with postcap rates in 2023 using Persistence to Basal Insulin, a health plan performance measure used in Medicare Part D quality programs, among the study population and multiple subgroups. RESULTS: A statistically significant increase (+1.3 percentage points; P < .001) was seen in overall patient persistence to basal insulin in the first year of the implementation of the insulin cost cap. Subgroup analyses showed greater increases in persistence in several subpopulations, including patients aged 45 to 54 and 65 to 74 years, male patients, non-Hispanic Black patients, and patients residing in certain census divisions, especially those with a high prevalence of type 2 diabetes. CONCLUSIONS: In addition to providing financial relief to Medicare patients, the implementation of the insulin cost cap was associated with an improvement in patients' treatment persistence to basal insulin therapy, a measure associated with positive health and economic outcomes. These results lend useful insight into future policy evaluations and proposals that seek to improve treatment access and address disparities in appropriate medication use.