Did Medicare Part D Affect National Trends in Health Outcomes or Hospitalizations? A Time-Series Analysis.

The broader implications of the Medicare prescription drug insurance benefit (Part D) are of national importance because the benefit substantially increased access to prescription drugs for more than 47 million older adults and adults with disabilities (1). Since its implementation in 2006, Part D has become so widespread that even patient groups who previously had drug coverage substantially increased their medication use (1); nonadherence related to difficulties in paying for medication also declined (2, 3). Medication use can influence health; however, little is known about the role of Part D in improving the health of the Medicare population, reducing the need for other medical services, or changing the efficiency of care. Several studies have detected encouraging reductions in spending on nondrug medical services after Part D implementation, but all used data from the early transition years (2006 to 2007) and were limited by a focus on population subgroups, particularly those who voluntarily enrolled to obtain drug coverage or more generous coverage (4). These self-selected enrollees were likely to differ from other subgroups in unmeasured ways and to be better prepared to take advantage of their new coverage. Their experience with Part D is probably more striking than that of the entire Medicare population on average. Medicare beneficiaries with limited or no drug benefits before 2006 saw statistically significant decreases in nondrug medical spending after enrolling in Part D (5, 6). Medicare hospitalizations decreased after Part D implementation in states where preimplementation drug coverage rates had been especially low (7). These associations in selected subgroups may not be generalizable to the larger Medicare population, however, because most of the population previously had drug coverage (8). Nevertheless, the U.S. Congressional Budget Office, partially in response to the subgroup evaluations, recently adopted a new costing method that assumes that increases in prescription fills at the full population level offset overall costs in other Medicare services (9). To address the lack of information about possible population-wide cost offsets associated with Part D, we estimated changes in health outcomes and medical services across the entire community-dwelling Medicare population to determine its comprehensive long-term policy effects. We used 11 years of survey data from the Medicare Current Beneficiary Survey (MCBS) (2000 to 2010 [latest data available]). To our knowledge, this is the only data set with nationally representative information on the health, functioning, and health service use of both the fee-for-service and Medicare Advantage populations. Medicare Advantage enrollees are a large and growing segment of the Medicare population, and they are missing in Medicare claims-based evaluations. We used a longitudinal study design with strong external validity for assessing the national implications of Part D (8). We hypothesized that, in the absence of Part D, population-level trends in health and medical services would have followed previously established trends; any statistically significant and consistent change in those trends after 2006 may be attributable to Part D.