JAMA Health Forum 12/10/2021

Aaron L. Schwartz, MD, PhD; Khalil Zlaoui, MS, MEng; Robin P. Foreman, PhD; Troyen A. Brennan, MD, JD, MPH; Joseph P. Newhouse, PhD

In this cohort study with a difference-in-differences analysis, during the first year of Medicare coverage, MA was associated with large reductions in institutional (Part A) utilization and spending.

Conclusions

This retrospective cohort study of a single private insurer demonstrates a differential reduction in inpatient spending and utilization associated with entering MA rather than TM; this finding suggests that private MA plans may lower inpatient spending and utilization relative to TM during the first year of Medicare coverage. The research also illustrates the feasibility of combining multiple sources of health insurance claims to examine how health care outcomes change as individuals move across types of health insurance. This approach has broad potential applications to investigate the effects of health insurance type on various outcomes of interest to physicians and policy makers.