Impact of Medicare Part D for Medicare-age adults with arthritis: Prescription use, prescription expenditures, and medical spending from 2005 to 2008




To evaluate the impact of Medicare Part D on medication utilization, drug expenditures, and medical expenditures in patients with arthritis.


This was a retrospective study using a national sample of 2,484 Medicare-eligible beneficiaries with arthritis from the pooled Medical Expenditure Panel Survey 2005–2008 data. Quantile regression was used to estimate the following outcomes: 1) number of prescription fills, 2) total drug expenditures, 3) out-of-pocket (OOP) drug expenditures, 4) Medicare-paid drug expenditures, 5) total medical expenditures (including all payments for inpatient/outpatient care, prescription drugs, and other medical services), 6) OOP medical expenditures, and 7) Medicare-paid medical expenditures. For each outcome variable, the 50th, 75th, and 90th percentiles were estimated, adjusting for demographics and comorbidity. All expenditures were inflation adjusted to 2008 dollars.


From 2005 to 2008, the adjusted median annual number of prescription fills increased by 4.2 (14.6% change), from 28.4 to 32.6. The adjusted median OOP drug expenditures and OOP medical expenditures decreased by $151 (25.2% change) and $197 (17.3% change), respectively. The adjusted median Medicare-paid drug and medical expenditures increased by $366 and $896 (39.5% change), respectively. The adjusted total prescription expenditures increased by $845 (25.3% change) at the 75th percentile and by $1,194 (22.0% change) at the 90th percentile. The adjusted total medical expenditures did not change significantly.


Medicare Part D resulted in increased medication utilization and significant reductions in OOP drug and OOP medical expenditures among beneficiaries with arthritis 3 years after its implementation. Part D was not associated with significant differences in total medical spending.