Impact of Medicare Part D on prescription use, health care expenditures, and health services utilization : national estimates for Medicare beneficiaries and vulnerable populations, 2002 to 2009

textThe purpose of this study was to investigate the impact of Medicare Part D on prescription utilization, health services utilization, and health care expenditures in the general Medicare population – as well as Medicare sub-populations, including non-Hispanic blacks (NHBs), Hispanics, near poor individuals, and persons with higher disease burden. A retrospective analysis of Medicare beneficiaries (N=32,228) was conducted using the Medical Expenditure Panel Survey 2002 to 2009 data. Multivariable quantile regression was used to estimate the following outcomes, adjusting for socio-demographic characteristics: 1) number of prescription fills; 2) out-of-pocket (OOP) drug expenditures; 3) total drug expenditures; 4) OOP health care expenditures; 5) total health care expenditures; 6) number of hospitalizations; and 7) number of emergency department (ED) visits between the pre-Part D (2002-2005) and post-Part D (2006-2009) periods. All expenditures were inflation-adjusted to 2009 dollars. The average age of the study sample was 71.0 (SD=14.5). In the general Medicare population, Part D was associated with decreases in OOP drug expenditures (-25.7% to -33.6%; p<0.0001) and OOP health care expenditures (-22.1% to -24.3%; p<0.0001) as well as increases in the number of prescription fills (5.8% to 8.4%; p<0.0001) and total drug expenditures (75th percentile: 5.5%; 90th percentile: 10.2%; p