Presentation (CTI)

OBJECTIVES: Prior studies show significant changes in prescription medication use with the onset of COVID-19, varying by insurance type. Whether these differences stem from insurance design or patient characteristics remains unclear. Using a regression discontinuity design, this study evaluates the causal effects of Medicare versus commercial insurance on pandemic-related changes in medication use. We analyzed overall utilization per member-month, as well as retail, physician-administered, and specific therapeutic classes like psychotropics, antibiotics, antivirals, cardiometabolic, and oncology drugs.
METHODS: A regression discontinuity design was applied to Colorado All-Payers Claims Data (N=498,906) for individuals aged 55 - 75 with commercial or Medicare insurance (January 2019 - December 2021). The running variable was age relative to the Medicare eligibility threshold (65 years). Separate pre- and post-COVID analyses estimated changes in prescription fill rates, expressed as prescriptions per member-month. Regression models included interaction terms for Medicare eligibility and the COVID-19 period, with clustering at the individual level to account for within-person correlations.
RESULTS: A total of 21,528,605 claims were analyzed, with 15,342,930 claims (71.3%) from individuals with commercial insurance and 6,185,675 claims (28.7%) from individuals with Medicare. Medicare eligibility significantly increased prescription fill rates compared to commercial insurance across all therapeutic classes in the pre-COVID period (e.g., psychotropics: β = 0.4719; 95%CI: 0.4605, 0.4833; p<0.001, and antibiotics: β = 0.3593, 95%CI: 0.3504, 0.3683, p<0.001). During the COVID-19 pandemic, Medicare's protective effect was consistently reduced across all analyzed categories, with the most pronounced attenuation observed for retail drugs (β = -0.4674, 95%CI: -0.4820, -0.4527; p<0.001).
CONCLUSIONS: Medicare eligibility enhances prescription drug access, but its protective effect was attenuated during the COVID-19 pandemic, exposing vulnerabilities in the healthcare system. These findings are important to consider when implementing policy measures to strengthen prescription drug access and ensure care continuity for the Medicare-eligible population during future public health emergencies.