BACKGROUND: Medicare Part D increased economic access to medications, but its effect on population-level health outcomes and use of other medical services remains unclear.

OBJECTIVE: To examine changes in health outcomes and medical services in the Medicare population after implementation of Part D.

DESIGN: Population-level longitudinal time-series analysis with generalized linear models.

SETTING: Community.

PATIENTS: Nationally representative sample of Medicare beneficiaries (n = 56,293 [unweighted and unique]) from 2000 to 2010.

MEASUREMENTS: Changes in self-reported health status, limitations in activities of daily living (ADLs) (ADLs and instrumental ADLs), emergency department visits and hospital admissions (prevalence, counts, and spending), and mortality. Medicare claims data were used for confirmatory analyses.

RESULTS: Five years after Part D implementation, no clinically or statistically significant reductions in the prevalence of fair or poor health status or limitations in ADLs or instrumental ADLs, relative to historical trends, were detected. Compared with trends before Part D, no changes in emergency department visits, hospital admissions or days, inpatient costs, or mortality after Part D were seen. Confirmatory analyses were consistent.

LIMITATIONS: Only total population-level outcomes were studied. Self-reported measures may lack sensitivity.

CONCLUSION: Five years after implementation, and contrary to previous reports, no evidence was found of Part D's effect on a range of population-level health indicators among Medicare enrollees. Further, there was no clear evidence of gains in medical care efficiencies.