Weighing the Impacts of GLP-1s: Quasi-Experimental Evidence From Provider Adoption

The arrival of GLP-1 medications has been described as one of the most important health care innovations in recent years. We provide large-scale quasi-experimental evidence on their real-world impacts by exploiting variation in the eventual prescribing propensities of patients’ pre-existing primary care providers. Using a panel intent-to-treat design, we compare outcomes for 1.4 million diabetic or obese veterans based on their 2018 provider’s eventual propensity to adopt GLP-1s, leveraging comprehensive electronic health records and biomarker data from the Veterans Health Administration, a setting with minimal insurance attrition and low-cost access to these drugs. Patients whose providers become higher propensity adopters experience substantial improvements in glycemic control and clinically meaningful weight loss; our treatment-on-the-treated estimates closely match estimates from clinical trials. Despite these metabolic benefits, we find no statistically significant effects on emergency department utilization, mental health and substance use outcomes, or non–GLP-1 medical spending through 2024.