Insulin Affordability: Unpacking the Impact of the Inflation Reduction Act on Diabetes Outcomes and Equity in Medicare - ABSTRACT The list price of insulin has increased dramatically over the past two decades, hindering access to this essential medication, contributing to insulin rationing and ultimately worsening health outcomes for people living with type 1 (T1D) and type 2 diabetes (T2D). To address insulin affordability for Medicare beneficiaries, the Inflation Reduction Act (IRA) capped out-of-pocket (OOP) payments for one month's supply of insulin to $35 for all Medicare beneficiaries enrolled in Medicare Part D plans effective 2023. Understanding the impact of IRA provisions on patients' OOP payments for insulin, health outcomes, and disparities in diabetes care is crucial to advancing effective and equitable solutions to structural barriers in diabetes care. Accordingly, we propose to evaluate the real-world implications of the IRA by leveraging rigorous quasi-experimental methods applied to data from OptumLabs Data Warehouse linked with Medicare fee-for-service (100% sample) claims from 2021-2022 (pre-IRA) and 2023-2024 (post-IRA). These data include both utilization and clinical information for beneficiaries in traditional Medicare and Medicare Advantage plans across the U.S., as well as those who are commercially insured (for comparison), with characteristics of each prescription plan (benefit design, including Senior Savings Model participation prior to IRA), OOP payments for each medication, and clinical data (diagnoses, procedures, clinical encounters, prescription medication fills, and even laboratory data such as hemoglobin A1c levels). Using this rich and comprehensive nationwide data asset, we will address the following aims: AIM 1: To examine the association between IRA implementation and patient OOP payments for insulin by comparing pre- and post-IRA trends among Medicare beneficiaries (separating those who participated in the Senior Savings Model vs. those who did not), then comparing them to corresponding trends among commercially insured patients 60-64 years. AIM 2: To examine the association of IRA implementation and clinical outcomes in the same patient subgroups, including rates of insulin use, type(s) of insulin used, insulin adherence, utilization of non-insulin guideline-recommended T2D diabetes medications (e.g., SGLT-2 inhibitors and GLP-1 receptor agonists for those with T2D), hemoglobin A1c levels, and rates of hospitalizations and emergency department visits for hypoglycemic and hyperglycemic emergencies. AIM 3: To examine the association of IRA implementation with sociodemographic disparities in diabetes care and outcomes (from AIM 1 and 2) among subgroups defined by sex, race/ethnicity, rurality, and Social Deprivation Index. By evaluating the effectiveness of this landmark policy, we aim to inform future healthcare policy decisions about prescription drug affordability and contribute to improving the lives of individuals living with T1D and T2D in the United States.
