Veterans Affairs Study of a Real-World Inhaler Delivery Device Transition on Climate and Health Outcomes (VA-SWITCH)

PROJECT ABSTRACT Background. Combination inhaled-corticosteroid/long-acting beta-agonist (ICS/LABA) inhalers are a mainstay for controlling respiratory conditions such as asthma and chronic obstructive pulmonary disease (COPD). These inhaled medications can be delivered to the patient with a metered-dose inhaler (MDI) or a dry-powder inhaler (DPI). Although the active ingredients of MDI and DPI inhalers are similar, the mode of drug delivery is different, and there are limited real-world data on their comparative effectiveness. Additionally, MDIs have a disproportionate environmental toll because they use hydrofluorocarbon aerosol propellants with high global warming potential. A global phase-down of hydrofluorocarbons to reduce greenhouse gas emissions will likely result in disruptions to the inhaler aerosol market, further underscoring the importance of developing evidence- based guidelines to inform clinical decision-making. A 2021 Veterans Health Administration (VHA) national formulary change provides a unique opportunity to assess both the clinical outcomes and the net environmental impacts of a switch from MDI to DPI inhalers in a national cohort of adults with a high burden of respiratory disease. Specific Aims: (A1) Test the real-world clinical effectiveness of metered-dose vs dry- powder ICS/LABA controller inhaler therapy. (A2) Identify patient and facility factors associated with successful conversion from MDI to DPI controller therapy. (A3) Estimate the greenhouse gas emissions avoided under a variety of inhaler prescribing scenarios. Impact: Our results will assess the impact of the 2021 VHA formulary change on 181,524 Veterans impacted by the 2021 VHA formulary change and inform optimal inhaler prescribing to maximize control of common respiratory diseases while minimizing the environmental impact of care. Innovation: Our study is innovative because it leverages a large natural experiment (2021 VHA formulary change) and addresses under-studied topics (real-world clinical effectiveness of MDI vs DPI therapy; the climate impact of healthcare). Methods: In a national cohort of 181,524 patients switched from metered- dose to dry-powder ICS/LABA under the 2021 VHA formulary change, we will use a within-person study design to test the clinical effectiveness of metered-dose vs dry-powder ICS/LABA therapy. Clinical outcomes will include albuterol fills, prednisone fills, and healthcare utilization. We will identify patient and facility factors associated with successful conversion from MDI to DPI controller therapy using a sequential mixed methods study design. We will complete life-cycle assessments to quantify the environmental impact of inhalers on the VHA formulary; calculate the greenhouse gas emissions averted by the VHA formulary change; and estimate the greenhouse gas emissions that could be avoided under a variety of scenarios for optimizing inhaler therapy.