Medicare Part D and Hospital Admissions due to Antimicrobial Resistance.

Antimicrobial resistance (AMR) has been increasing rapidly in the United States despite government efforts to contain its spread. Both under-utilization and overuse of prescribed antimicrobials contribute to rising resistance. The introduction of Medicare Part D in 2006 expanded prescription drug coverage for the elderly, including coverage for antimicrobial medications. If cost barriers had previously led to under-utilization of prescriptions, then Medicare Part D could have mitigated AMR by improving access to antimicrobials. However, if Medicare Part D also encouraged excessive antibiotic use, it may have inadvertently contributed to greater resistance. Using data from the Nationwide Inpatient Sample (NIS), Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality for January 2001 to September 2008, I estimate the causal impact of Medicare Part D on AMR-related hospital discharges using a difference-in-differences identification strategy. My findings suggest that Medicare Part D led to a slower increase in AMR-related inpatient discharges among the Medicare-eligible population.